Widebody kit and vehicle registration: the process you need to know

A wide body kit radically transforms the appearance of a vehicle: wider bumpers, more aggressive side skirts, integrated fender flares. It is one of the most spectacular aesthetic modifications in the tuning world — and also one of those that raises the most administrative questions. Do you need to update your registration certificate after installing this type of kit? What is the exact procedure, who should you contact, and how long does it take?

This guide focuses exclusively on the administrative procedure: what service-public.fr says, how individual approval works with the DREAL, what documents to gather, and in which cases this process is actually necessary or, on the contrary, superfluous. We do not detail the mechanical installation of the kit here (already covered in our other guides), but rather the complete administrative process, from the initial inquiry to the updated registration certificate.

Many owners discover this administrative requirement too late, once the kit is already installed, while preparing for their technical inspection or coming across a forum that mentions the issue. Our goal with this guide is to reverse this order: to give you all the keys to the procedure before purchase, so that you can decide with full knowledge of the facts whether the project is worth the investment of time and money it entails, or if a more modest kit, which remains within the original dimensions, equally meets your desire for customization without this administrative process.

Wide body kit: what exactly are we talking about?

There is actually a wide range of products grouped under the term "body kit," which must be distinguished before talking about administrative procedures. At one end, we find sport bumper kits (front lip, rear diffuser, side skirts) that replace the original elements with a visually more aggressive version, without changing the overall width of the vehicle. This is the case for the majority of our kits, such as the Toyota C-HR body kit that combines a front lip and rear diffuser in the vehicle's original spirit. At the other end, we find true wide body kits, which incorporate structural fender flares and actually widen the vehicle's dimensions by several centimeters on each side, in the spirit of Liberty Walk preparations or the carbon kits installed on supercars like the Lamborghini Urus.

This distinction is the starting point of any administrative consideration: a bumper kit that remains within the vehicle's original dimensions follows a very different logic from a kit that actually widens the bodywork. It is this second category, the most visually ambitious, that is at the heart of this guide on the registration certificate update procedure.

Do you need to update the registration certificate? The decision table according to the type of kit

Why the registration certificate sometimes needs to be updated

The registration certificate, or registration certificate, describes the administrative identity and some of the approved technical characteristics of your vehicle — but it does not carry any dimensions: neither length, nor width, nor height. The only physical measurements found there are masses (G, vehicle operating mass; G.1, empty weight; F.2, maximum permissible operating load, the PTAC in the usual sense), and the J, J.1, J.2 and J.3 sections indicate the type and bodywork, not a measurement. The approved overall width is found in the vehicle approval documents: certificate of conformity, descriptive manual, approval report. When a body modification significantly changes this approved characteristic compared to the original approval sheet, French regulations, according to service-public.fr, provide that the owner must in principle have this modification certified and update their registration certificate accordingly. This obligation does not concern minor aesthetic modifications that do not change the approved measurements, but rather substantial transformations — and a true wide body kit that widens the vehicle by several centimeters typically falls into this category.

The reasoning behind this obligation is simple: the registration certificate must reflect the physical reality of the vehicle on the road, especially for the needs of technical inspection, insurance, and road safety in general (a vehicle significantly wider than what is indicated on its technical sheet can, for example, raise questions about its compatibility with certain safety equipment or its dimensions in case of a roadside check).

Does my body kit change the overall width?

Body kit installed	no, original dimensions
yes, widened	No update required
Likely declaration	Sport bumper kit,
classic lip, diffuser	True wide body kit,
structural flares	→ DREAL RTI procedure

The exact role of the DREAL and the approved technical body

To properly understand the procedure, it is useful to clarify the role of each of the actors involved. The DREAL is the administrative authority that processes your request and ultimately issues the individual approval report. It does not perform the physical technical verifications of the vehicle itself, but relies, for the files that require it, on approved technical bodies (such as the UTAC, the technical union of the automobile, motorcycle and cycle, or other authorized equivalent services) that carry out the concrete examination of the modification: verification of the mounting points, structural resistance, absence of interference with the vehicle's safety elements (braking, steering, lights, license plate).

This division of roles explains why the overall timeframe of the procedure depends both on the administrative workload of the DREAL and on the availability of the technical body to perform the physical verification of the vehicle, which generally requires an appointment and a trip of the vehicle to an authorized center. This is a point to integrate into your planning: the vehicle must be physically presented, kit already installed, for this verification step, which means that the installation must be finalized before this part of the procedure can begin.

Individual approval: the step-by-step procedure

If your kit significantly modifies the approved dimensions of your vehicle, the procedure to follow is called individual approval (RTI). Here is its process, in order.

Step 1 — Preliminary inquiry. Even before buying the kit, contact the DREAL (Regional Directorate of the Environment, Planning and Housing) of your region to explain your project and confirm that an RTI is indeed necessary in your case. The contact details of the competent DREAL are available on the service-public.fr website or on your prefecture's website.

Step 2 — File preparation. The DREAL will communicate the list of documents to be provided, which generally includes: the current registration certificate, a descriptive manual of the modification (provided by the manufacturer or the kit installer), photographs of the modified vehicle, and depending on the case, a technical verification report established by a designated technical service.

Step 3 — Technical inspection. Depending on the extent of the modification, the DREAL may require inspection by an approved technical body (such as UTAC or an equivalent service), which checks, among other things, that the modification does not compromise the safety of the vehicle (braking, steering, visibility, structural strength of the mounting points).

Step 4 — DREAL application review. Once the complete application has been submitted, the DREAL reviews the request. The processing time varies depending on the region and the complexity of the application, but generally takes several weeks to a few months.

Step 5 — Certificate of acceptance. If the application is accepted, the DREAL issues a certificate of acceptance for a single modification, an official document certifying that the modification complies with regulations.

Step 6 — Registration document update. With this certificate, you must then apply to update the vehicle registration document (now done online via the ANTS website) so that the vehicle's new characteristics are officially recorded.

Budgeting a full wide-body project: beyond the price of the kit alone

One of the most useful lessons for anyone considering a genuine wide-body kit is to include all costs from the outset, beyond the purchase price of the wheel arch extensions or body kit alone. The kit itself often represents the most visible part of the budget, but is far from the only one. Professional installation, especially for a structural modification that permanently affects the bodywork, should be entrusted to an experienced installer rather than attempted as a DIY project, which represents a significant labor cost depending on the complexity of the kit. The administrative procedure fees themselves — the DREAL application review and, if applicable, technical inspection by an approved body — add to this budget, as do the time spent compiling the application and any travel required for the physical inspection of the vehicle.

Finally, an often-overlooked cost: the potential impact on your insurance premium once the modification has been officially declared. A vehicle whose dimensions and equipment value have changed significantly may have its premium reassessed by the insurer, which is normal since the insured risk itself has changed. Anticipating all these costs before you start will help you avoid unpleasant surprises and allow you to objectively compare the total cost of a genuine wide-body project with that of a much more modest sport bumper kit that remains within the original dimensions.

Documents to gather before contacting the DREAL

To save time and avoid back-and-forth, here are the documents we recommend preparing before even making initial contact with the DREAL:

— The vehicle's current registration document, with all original specifications clearly identified.

— The technical specifications of the body kit you are considering, including its precise dimensions (added width on each side, material, weight).

— The purchase invoice or, failing that, a detailed quote for the kit and its installation.

— Photographs of the vehicle before modification, useful for establishing a clear comparison during the application review.

— The contact details of the professional installer if the installation is carried out by a garage, which may be able to certify that the installation complies with regulations.

Typical documents to gather for a single modification acceptance

Supercars and exceptional vehicles

On high-end vehicles such as the Lamborghini Urus or other supercars, premium carbon fiber wide-body kits are particularly sought after for their spectacular appearance. In this segment, the value of the vehicle and the extent of the investment in the kit further reinforce the importance of a rigorous administrative process from the outset: a vehicle of this value deserves impeccable conformity, both for its future resale and for peace of mind when driving it every day. Owners of this type of vehicle generally have access to specialized preparers accustomed to single modification acceptance procedures for ambitious projects, which can make compiling the technical application easier than with a general installer.

However, this does not change the general principle explained in this guide: it is the technical nature of the modification, not the value or brand of the vehicle, that determines whether the single modification acceptance procedure is necessary. A wide-body kit on a supercar follows exactly the same administrative logic as an equivalent kit on a more modest vehicle — only the overall budget and the available professional support differ in practice.

Kits that generally do not require declaration

It would be a mistake to think that every body kit requires this lengthy procedure. This is not the case for the majority of the products we sell. A sport bumper kit that replaces the original bumper with a more aggressive version, such as our Toyota C-HR body kit (front blade + rear diffuser), generally remains within the vehicle's original approved dimensions: it does not change the overall width and therefore generally does not require declaration at the prefecture or a single modification acceptance. It remains, of course, subject to the standard mounting and safety rules checked during the technical inspection, but not to the registration document update procedure described in this guide.

The dividing line is therefore clear: it is the actual widening of the vehicle's dimensions that potentially triggers the declaration requirement, not a simple change in the style of a bodywork element that remains within the original dimensions. Before making any purchase, check the product's technical specifications to see whether it changes the overall width of your vehicle — this is the key piece of information to determine which side of this dividing line your project falls on.

Deadlines, costs and contacts: what to anticipate

The single modification acceptance procedure is neither free nor instantaneous, and it is best to know this before purchasing an ambitious kit. Deadlines vary greatly depending on the region and the DREAL workload, but generally take several weeks to a few months between submitting the complete application and obtaining the certificate of acceptance. Costs include the DREAL application review fees (which vary by region) and, if applicable, the technical inspection fees by an approved body if required. In addition, of course, there is the cost of the kit itself and its professional installation, which is strongly recommended for this type of structural modification.

In terms of contacts, your first point of contact remains the DREAL in your region, whose contact details can be found on service-public.fr. Some professional installers specializing in tuning are accustomed to this type of procedure and can assist you in compiling the application — this is a service that may be worth the extra cost if your project is ambitious, as the procedure can seem complex to someone approaching it for the first time.

Why deadlines and requirements vary from one region to another

A question we are often asked: why does the procedure seem faster in some regions than in others? The answer lies in the very organization of the DREAL, which are regional decentralized services rather than a single centralized administration. Each DREAL manages its own volume of applications, with teams and resources that vary by region, which explains the different application review times from one region to another. It is not a matter of different rules — the national regulatory framework applies everywhere in the same way — but rather a matter of workload and local organization.

This variability is another reason to contact your DREAL as early as possible in your project, ideally even before purchasing the kit, to get a realistic estimate of the deadlines in your region and to be able to plan your project accordingly. A local professional installer accustomed to the applications in their region can often give you a more accurate estimate than a theoretical national average.

Practical case: wide-body kit on a premium SUV vs. sport bumper kit on a city car

To illustrate the difference between the two categories of kits mentioned above, let's take two typical examples from our catalog. The Toyota C-HR body kit (front blade and rear diffuser) transforms the vehicle's appearance without affecting its approved overall width: once this type of project is installed by a professional in compliance with the original mounting points, it generally requires no procedure with the DREAL and simply presents itself at the next technical inspection like any other standard bodywork modification.

Conversely, a project combining structural carbon fiber wheel arch extensions on a vehicle such as the BMW M3 G80, with a real and visible widening of several centimeters on each side, typically falls within the scope of the single modification acceptance described in this guide. The difference between the two projects is not a matter of price range or vehicle brand, but rather the technical nature of the modification: does the overall width really change, yes or no? This question, and this question alone, determines whether you need to undertake the full administrative procedure or not.

The most common mistakes in conformity procedures

Mistake no. 1: purchasing the kit before inquiring with the DREAL. This is by far the most costly mistake: investing several thousand euros in a full wide-body kit before knowing whether the project is administratively feasible under reasonable conditions for you, or before having an estimate of the procedure's deadlines and costs.

Mistake no. 2: underestimating the application review time in your schedule. If you plan to drive the modified vehicle for a specific event (meet, show), a deadline of several months for the single modification acceptance can compromise this schedule if the procedure is not started sufficiently in advance.

Mistake no. 3: not keeping a record of the vehicle's original configuration. Photographs taken before modification, kept from the outset, greatly facilitate the application review and the before/after comparison requested by the DREAL.

Mistake no. 4: having the kit installed by an installer not accustomed to this type of application. An installer who understands the requirements of the single modification acceptance can guide the installation to facilitate the subsequent technical inspection (accessibility of inspection points, photographic documentation during installation), which is not always the case with a general installer.

Mistake no. 5: thinking the procedure is optional if the vehicle "looks inconspicuous". The declaration requirement does not depend on the discretion of the modification but on its actual technical extent compared to the approval sheet — a purely visual reasoning has no administrative value.

What happens if you do not follow the procedure?

Driving a vehicle whose dimensions no longer match those on the registration certificate without having completed the required update process exposes you to several types of risks. At the technical inspection, the inspector may notice the discrepancy between the physical vehicle and the characteristics listed on the registration certificate, which could lead to a remark or even a re-inspection if the inspector considers the modification significant and not supported by an official document. During a roadside check, law enforcement officers may also notice this administrative non-compliance. Finally, and this is often the most tangible point for owners, in the event of an accident, the insurance adjuster who notices a discrepancy between the vehicle and its registration certificate may cite an undeclared increase in risk, with a potential impact on compensation, especially if the modification is linked to the circumstances of the claim.

We stress that this procedure, although more cumbersome than a simple declaration, remains far preferable to these cumulative risks—especially for an aesthetic investment as significant as a full wide-body kit, where the financial stakes more than justify the time spent on administrative compliance.

Insurance: the link between the administrative procedure and your coverage

Beyond compliance at the technical inspection, updating the registration certificate has a direct impact on your insurance coverage. An automobile insurance policy is established based on the declared characteristics of the vehicle; a significant discrepancy between the actual vehicle and its registration certificate can be interpreted as an undeclared increase in risk, which can have consequences in the event of a claim, regardless of the issue of the technical inspection. This is why we recommend treating the RTI process and informing your insurer as two sides of the same coin: the RTI updates your official document, the declaration to the insurer updates your policy. Both are necessary for complete peace of mind.

In the interim between the installation of the kit and obtaining the acceptance report, we recommend contacting your insurer directly to inform them of the ongoing situation and to find out their exact position on the transition period. Some insurers require immediate declaration of any substantial modification, even before the finalization of the administrative procedure, while others wait for the final official document. This advance clarification saves you any unpleasant surprises in the event of a claim occurring during the processing of the file.

How we document our body kits to facilitate your process

On every body kit product sheet in our catalog, we specify whether the product modifies the vehicle's approved overall width or not, as well as the exact dimensions of any widening element when applicable. This information, combined with the invoice we provide you, constitutes a solid basis for any isolated acceptance file you may need to prepare. We also specify the material, the method of attachment, and the precise compatibility by vehicle generation, information that may be requested during the technical inspection by the approved body.

As with all our products with regulatory dimensions, we remind you that we cannot substitute ourselves for the DREAL or a road law professional to judge the exact necessity of an RTI on your specific vehicle. Our role is to provide you with the most complete and honest technical information possible, so that you can initiate your administrative process fully informed.

Our advice before buying a wide body kit

At Becquet Voiture, we systematically detail on every body kit product sheet whether the kit remains within the vehicle's original dimensions or actually widens them, as well as the precise dimensions of any widening element. Before buying an ambitious kit, we recommend: contacting the DREAL in your region to confirm the necessity (or lack thereof) of an RTI in your specific case, budgeting the full cost of the project by including the administrative procedure and not just the kit and its installation, choosing a professional installer accustomed to this type of structural mounting, and keeping all documentation (invoice, technical sheet, eventual acceptance report) that will be useful to you at every step, from the technical inspection to a possible resale of the vehicle.

After the RTI: the update process on the ANTS website

Once the isolated acceptance report is obtained, there is one last step: the actual update of your registration certificate. This process is now done exclusively online, via the website of the National Agency for Secure Titles (ANTS), which has taken over the management of registration certificates since the end of the prefectural counters dedicated to this formality. You will need to create or use your ANTS account, enter your vehicle's information, attach the acceptance report obtained from the DREAL as well as the other supporting documents requested (ID, proof of residence, old registration certificate), and then submit your modification request.

The processing time for this final step is generally faster than the processing of the RTI itself, but it should be taken into account in your overall schedule. Once the request is validated, you will receive a new registration certificate taking into account the new acceptance: the dimensions themselves remain recorded in the report, which is kept with the vehicle—it is only at this point that your administrative situation is fully regularized, from the body kit to the final official document.

Buying a used vehicle already equipped with a wide body kit

If you are considering buying a used vehicle already equipped with a wide body kit, the question of administrative compliance must be part of your evaluation criteria along with the general mechanical condition. Always ask the seller if the modification has been subject to an isolated acceptance and if the registration certificate has been updated accordingly. Since a registration certificate never bears dimensions, that is not where to look: ask for the isolated acceptance report, and check that the registration certificate does indeed bear the trace of this new acceptance. In its absence, as the new buyer, you will either have to initiate the regularization process yourself, or negotiate the purchase price accordingly to cover this additional cost and time.

Also check that the vehicle has a valid technical inspection that does not mention any remarks regarding the bodywork, which would be an additional warning sign about the compliance of the existing installation. In case of doubt, an inspection by a professional before purchase, including an opinion on the probable administrative compliance of the installed kit, remains the best way to secure your acquisition.

Frequently Asked Questions

Do all body kits require a registration certificate update?
No. Only kits that actually modify the vehicle's approved overall width (true wide body kits with structural flares) are concerned. A sport bumper kit that remains within the original dimensions generally does not trigger this requirement.

Who issues the isolated acceptance?
It is the DREAL (Regional Directorate of Environment, Planning, and Housing) of your region that processes and issues the isolated acceptance, based on a file that you prepare with, if necessary, the help of a professional.

How much does an isolated acceptance cost?
The cost varies by region and the nature of the modification, including the file processing fees and, if necessary, the technical verification fees by an approved body. We recommend asking for a precise quote directly from the relevant DREAL.

Can I drive while the RTI file is being processed?
This is a question to ask your DREAL and your insurer directly, as the answer depends on your specific situation and may vary. As a precaution, some owners wait until they obtain the acceptance report before driving the modified vehicle daily.

What happens if I resell a vehicle with an undeclared wide body kit?
The buyer inherits the vehicle's administrative situation. An unregularized discrepancy between the registration certificate and the physical vehicle can complicate the resale or expose the new owner to the same risks described in this guide—it is better to regularize before the sale.

Does a premium carbon wide body kit have a better chance of being accepted than a low-end kit?
Manufacturing quality affects the safety and solidity of the installation, criteria examined during the technical inspection. But it never exempts you from the administrative procedure itself, which applies in the same way regardless of the kit's price range.

Is the process different if the kit is installed by a professional rather than by myself?
The administrative procedure remains identical regardless of the installer. However, a professional accustomed to this type of file can facilitate the preparation of the technical file and sometimes speed up the verification step by providing installation documentation already structured for the approved body.

Can I initiate the RTI request myself or do I need to go through an intermediary?
You can initiate the process yourself directly with the DREAL. Some professional installers offer assistance in preparing the file, which can be useful if you are discovering the procedure for the first time, but it is not a regulatory requirement.

What should I do if my DREAL tells me that my project is not eligible for an RTI?
Some very major modifications can indeed exceed the scope of what an isolated acceptance allows. In this case, it is essential to review the scope of the project with your installer before any purchase, rather than discovering this limit after investing in the kit.

Is the procedure the same for a collector vehicle?
Collector vehicles may fall under special regimes depending on their age and administrative status. If your project concerns a collector vehicle, we recommend checking with the DREAL for any applicable specificities before initiating any standard process.

How can I know exactly what my approved overall width is?
Not on your registration certificate: this document does not contain any dimensions. The approved overall width is found on the certificate of conformity (COC) issued at the first registration, on the vehicle's descriptive notice, or in the manufacturer's technical documentation. It is this value, and not an approximate measurement made with a tape measure, that serves as the reference. Compare it to the final width announced by the kit manufacturer: if the total exceeds it, you enter the scope of isolated acceptance. In case of doubt about reading the document, the DREAL will be able to confirm the dimension to take into account.

Can I have the kit installed before preparing the file?
It is possible but not recommended. Installing it first deprives you of any feedback from the DREAL on feasibility and exposes you to having to remove the kit if a point gets stuck. The safest sequence remains: contact with the DREAL, preparation of the technical file, then documented mounting. You gain peace of mind and often overall time, even if the start seems slower.

Is a wide body kit installed abroad recognized in France?
An installation carried out outside of France does not exempt you from French requirements as long as the vehicle is registered in France. Foreign documents can support the file, but it is the DREAL that assesses their acceptability. Have this point checked beforehand if you are considering importing a vehicle already equipped: it is one of the situations that generates the most unpleasant surprises.

Why this guide focuses on the procedure rather than the technical installation

You will find other articles on our blog dedicated to the practical mounting of fender flares and body kits, with the tools and installation steps. This guide answers a different concern, often neglected until the last moment: that of the administrative compliance of the project, which should ideally be clarified before purchase rather than after installation. Many of our customers tell us they discovered the existence of isolated acceptance after having already invested in their kit, which forces them to initiate a process afterwards, sometimes in a hurry as a technical inspection approaches. By structuring your project in the reverse order—administrative information first, purchase later—you avoid this uncomfortable situation and approach your technical inspection with complete peace of mind, with a file already settled rather than to be regularized in a hurry.

Realistic timeline of a wide body project, from quote to registration certificate

Most owners underestimate not the difficulty of the procedure, but its total duration. Here is a realistic timeline, step by step, as we observe it on projects carried out seriously.

Phase 1: scoping and contact (1 to 3 weeks). Before any purchase, you identify the desired kit, you note the approved overall width in the vehicle's acceptance documents—certificate of conformity, descriptive notice, or manufacturer's technical documentation, never the registration certificate, which does not bear any—and you estimate the final width announced by the manufacturer. You then contact the DREAL in your region to find out the list of expected parts and the exact circuit. This phase costs nothing and determines everything else.

Phase 2: preparation of the technical file (2 to 6 weeks). This is generally the longest step, because it depends on third parties. Obtaining usable dimensioned plans from a manufacturer is the most frequent sticking point, especially on small-series kits. Anticipate this request from the moment you order the kit, and refuse to settle for a vague answer.

Phase 3: mounting (1 to 3 weeks). The installation itself is quick on a bolt-on kit, much longer when cutting, adjusting, and painting are required. Have the workshop document each step: photos, part references, mounting certificate. These elements directly feed your file.

Phase 4: processing and technical verification (variable by region). The DREAL examines the file and may request a visit before an approved technical body. This is the least predictable phase: depending on the service's workload and the complexity of the file, it can be quick or stretch over several months. A complete file from the start is the best accelerator.

Phase 5: update of the registration certificate. Once the acceptance report is obtained, you perform the modification request on the ANTS website by attaching this report. You then receive a registration certificate taking into account the new acceptance; the dimensions of the modified vehicle, however, remain recorded in the report, to be kept with the vehicle. The project is only administratively finished at that moment, and many owners wrongly stop at the previous step.

Above all, remember this: a properly carried out wide body project is measured in months, not days. This timeframe must be integrated from the start, especially if the vehicle serves you daily.

The full budget of a compliance update: the items that are forgotten

The price of the kit represents only a part of the actual budget. Here are the items that owners often discover along the way, and that it is better to integrate from the first quote.

Paint and fitting almost always constitute the first underestimated item. A kit delivered in primer requires careful preparation, exact color matching, and fitting of the bodywork gaps. On a multi-piece kit, this work frequently represents an amount of the same order as the kit itself.

Consumables and hardware come next: rivets, silentblocs, gaskets, mastic, adhesion primer. Taken separately these elements are modest, but their cumulative total is far from negligible on a full kit.

Tires and sometimes rims are the heaviest and most frequently forgotten item. A wide body kit only makes visual sense if the wheels fill the new arches. A set of rims of suitable diameter and offset, accompanied by tires of a larger section, can alone exceed the price of the kit.

Administrative fees include the file processing by the DREAL, the eventual visit before an approved technical body, and the modification of the registration certificate. They vary by region and the nature of the modification: only a quote from the relevant DREAL will give you a reliable figure.

Insurance premium adjustment, finally, is a recurring cost, not a one-off. A vehicle whose value and specificity increase will generally see its premium change. Ask your insurer for a quote before starting the project rather than discovering it afterwards.

Our advice: establish your budget by adding up these six items, then add a 15 to 20% safety margin. Widebody projects almost always have an adjustment surprise, and this margin prevents interrupting the project halfway through. For setups that remain within the original dimensions and do not involve any of these procedures, see our guide body kit and sport bumpers: are they legal in France.

Overall width and registration certificate: the box everyone is looking for does not exist

“overall vehicle width registration certificate” is one of the most searched queries on this subject, and it is based on a false belief. The French registration certificate follows the harmonized European format: it contains the vehicle's identity, its owner, its engine, its emissions, its masses — and no dimensions. Neither length, nor width, nor height. Looking for the overall width on your registration certificate is looking for a box that was never planned.

The only physical quantities printed on the document are masses, and that is precisely what fuels the confusion: you read kilograms, and you deduce that you will also read millimeters. Here is what the sections we most often mistake for dimensions actually contain.

F.1 — mass at technically permissible maximum load, the one the manufacturer has approved.
F.2 — mass at permissible maximum operating load in the Member State: this is what common language calls the GVWR.
F.3 — mass at maximum load of the whole assembly, vehicle and attached trailer.
G — mass of the vehicle in operation.
G.1 — national curb weight.
J, J.1, J.2 and J.3 — vehicle category, national type, bodywork in the community sense and national bodywork designation. These are labels (sedan, estate, van), not measurements.

Where the dimension is read, and where it is not

The practical consequence is simple: to know if your project exceeds the approved dimensions, the reference to compare is that of the certificate of conformity or the descriptive notice, not that of the registration certificate. If you no longer have them, the manufacturer or its network can reissue a COC, and the DREAL knows how to retrieve the acceptance dimension of the type concerned.

This does not dilute the obligation in any way. What triggers the procedure is not the fact that a box changes on a document, it is that an approved characteristic no longer corresponds to the vehicle on the road. This is the meaning of article R321-16 of the highway code: a notable modification requires a new acceptance. Overall width is simply the characteristic affected by a real widebody kit.

CE acceptance, national acceptance, isolated acceptance: three different things

Many discussions get bogged down because the word “approval” is used for three procedures that have neither the same recipient, nor the same object, nor the same counter. Distinguishing them saves weeks, and avoids asking the DREAL for something it does not issue.

Who issues what, and to whom

• CE acceptance by typeIt concerns a TYPE of vehicle and it is issued TO THE MANUFACTURER, never to an owner. In France, the authority that issues it is the CNRV, based on tests carried out by designated technical services — the UTAC is the best known of them. It is this acceptance that sets the overall width of your model.
• National acceptanceSame logic, French-French scope, for vehicles or series that do not fall under the community framework. It remains a matter for the manufacturer or the manufacturer-bodybuilder, not for individuals.
• Isolated acceptance (RTI)It concerns A single vehicle, identified by its serial number, and it is the only one of the three that is addressed to the owner. It is processed and issued by the DREAL of your region. It is the path for any wide body kit.
• The technical service is not the authorityAn organization like the UTAC carries out or verifies tests; it does not issue your title. Confusing the two wastes time: you do not “make an appointment at the UTAC” to have your kit approved, you open a file with the DREAL, which will say if a technical verification is necessary and by whom.

This hierarchy also explains why a kit sold as “approved” does not exempt you from anything when it widens the bodywork: the mention refers to the conformity of the part (material, absence of sharp edges, fit), not to the acceptance of the vehicle that receives it. We detail this commercial vocabulary in our guide approved tuning accessory: recognize what really commits you.

Two neighboring guides deal with the complementary sides of the same subject and share exactly the same regulatory basis: body kit and sport bumpers, are they legal in France for setups that remain within the dimensions, and fender flares and wheel spacers face the law and technical inspection for the boundary between the two families of parts.

RTI file and acceptance report: what the documents really contain

“dreal rti file”, “dreal rti file pdf”, “isolated acceptance report”, “isolated acceptance request”: internet users are looking for the parts, not the theory. The typical file table appears above in this guide; what is most often missing is knowing what each document looks like and why the DREAL requires it.

What the DREAL really reads in your file

• The descriptive notice of the kit: it must give the thickness per side, in millimeters, and the material. A commercial sheet is not enough.
• The dimensioned plans: this is the most often missing piece, and the one that blocks the most files. Ask the manufacturer for it BEFORE buying.
• The mounting method: bolted to original points, glued, riveted, or bodywork cut and remade. This point changes the scope of the verification.
• Before and after photos, in daylight, from several angles, wheels turned to show the range of motion.
• The invoice for the part and, if the installation is professional, the installation invoice with the certificate of conformity of the mounting.
• The request form specific to your DREAL: the models circulate in PDF on the regional sites, and they are not strictly identical from one region to another.

At the end of the journey, the document that counts is the acceptance report. It is this, and only this, that carries the characteristics of the modified vehicle — including the new overall width. The registration certificate you will receive afterwards will take into account this new acceptance, but it will not reprint the dimensions: they have no box to go into. Hence a simple and often neglected rule: the report is kept with the vehicle, it is passed on to the buyer in case of resale, and it is the piece to produce if a technical inspector or an insurer questions the dimensions.

A word on the mentions that we come across in the search results: “vasp rti file”, “caravan rti”. The VASP acronym designates specialized self-propelled vehicles — converted campers, vehicles for transporting people with reduced mobility. These files go through the same door, the DREAL, but they fall under a change of type, which has nothing to do with a bodywork widening on a passenger car. Do not take a VASP form as a model.

Price of an isolated acceptance: why no national rate circulates

“isolated acceptance price”, “dreal rti price”, “registration certificate modification price” form one of the biggest search clusters on the subject — and it is precisely the question that no serious site can answer with a single figure. Here is why, item by item.

The cost of an RTI is not a rate, it is an addition of distinct services. The processing of the file by the DREAL, the possible verification by a technical service, the establishment of the dimensioned plans by the manufacturer or the workshop, the documented installation, then the modification tax of the registration certificate are neither invoiced by the same actor, nor fixed in the same place. The registration certificate part also depends on the regional fiscal horsepower, whose rate is voted by each regional council and changes from one year to another.

Add that the scope of the technical verification — the heaviest and most variable line — depends on your setup: fenders bolted to original points and a bodywork cut and remade do not require the same examination. Two visually similar projects can therefore cost from simple to multiple in procedure.

This is the reason why we do not publish a range: an invented figure would make you build a false budget. The right approach consists of two calls. The first to the DREAL of your region, which will tell you if a technical verification is necessary in your case — this is the point, and not the rest, that tips the budget. The second to your installer, to quote the dimensioned plans and the documented installation. For the part that concerns us, the technical documentation of our parts, our customer service provides upon request the elements we have; the dimensions and notices come from the manufacturer, and it is up to them for the validity of what will be uploaded to the file.

As a rough order of magnitude dated on the only part we control — the price of the parts, recorded on August 12, 2026 in our catalog — a complete bumper kit that remains within the dimensions is around €599 for the Toyota C-HR body kit, a single front lip around €149, while a set of carbon fender flares for BMW M3 G80 exceeds €830. These amounts change: the product sheet of the day is authoritative, not this article.

“Wide kit” on youngtimers: E36, E46, Golf 4, 205, 306 — the vocabulary and the law

Google Suggest is unambiguous: behind the expression “wide kit” hides an entire youngtimer universe — wide kit E46 (sedan, touring, compact, coupe, phase 2), wide kit E36, wide kit Golf 4, wide kit 205, 306, 106, Twingo 1, E39. The same setups are searched in English under “wide body kit”: wide body kit BMW E46, E36, E90, F30, F32, M4. It is the same object, and therefore exactly the same administrative regime as described in this guide.

One point deserves to be said clearly, because it comes back in all youngtimer forums: the age of the vehicle creates no exemption. A widened 205 or E36 falls under the same isolated acceptance as an M3 G80. The collector vehicle status, however, obeys its own rules that must be checked on a case-by-case basis with the DREAL — and it is not obtained simply because a car is thirty years old.

Second point, more subtle and even more frequent: the confusion between fender flare and wheel spacer. These are two unrelated parts, and searches mix them permanently (“wheel spacer 4x108”, “wheel spacer 5x112”, “wheel spacer 20 mm”, versus “Nissan Juke fender flare”, “Ford Ranger fender flare”, “Renault Captur fender flare”).

Two parts, two logics

A wheel spacer does not modify the overall width of the bodywork; however, it can make the tire protrude from the wheel arch, which becomes a point of attention at the technical inspection and a safety question if the spacer is not dimensioned for the offset and the stud length. It is a subject in its own right, treated in our guides wheel spacers: utility, safety, legality and fender flares and wheel spacers face the law. For the choice of materials and the installation method of a real wide kit, see carbon fender flares: materials, installation and compatibility.

Finally, a useful reminder for those who come here looking to secure the whole of their preparation: spoilers and wings obey, them, a different logic from that of the dimensions — they are addressed in spoiler and wing at the technical inspection.

Individual approval and registration certificate: 12 short answers

Twelve questions that come up before every wide body project, all revolving around the same reflex: knowing which document says what, and at which counter it is requested.

Is my car's width written on the registration certificate?

No. The registration certificate does not contain any dimensions: neither length, nor width, nor height. The only physical quantities it carries are masses (G for the mass in running order, G.1 for the unladen weight, F.2 for the maximum permissible mass in running order, commonly called GVW). The approved overall width can be found on the certificate of conformity, the descriptive notice or the manufacturer's technical documentation.

What do boxes J, J.1, J.2 and J.3 contain then?

Designations, not measurements: the vehicle category, the national type, the bodywork in the EU sense and the national bodywork designation. You will find "saloon", "estate" or "van", never a number of millimeters.

What text requires a new approval after a wide body kit?

Article R321-16 of the Highway Code: a vehicle that has undergone a significant modification must undergo a new approval. A real widening of the bodywork falls into this category; a sport bumper that remains within the original dimensions, not.

Who processes and issues the individual approval?

The DREAL in your region, from the submission of the file to the issuance of the report. It is the only one of the three approvals (EC by type, national, individual) that is addressed to a vehicle owner.

Can the UTAC directly approve my kit?

No. The UTAC is a technical service: it carries out or verifies tests, it does not issue your title. In France, the EC approval by type is issued to the manufacturer by the CNRV on the basis of these tests; your individual approval, however, comes from the DREAL.

How much exactly does an individual approval cost?

No national price is published, because it is not a price but an addition: file processing, possible technical verification, dimensioned plans, documented installation, then the registration certificate modification tax, which depends on the fiscal horsepower approved by your region. Ask your DREAL and your installer for an estimate before buying anything.

What is the document most often missing in a file?

The dimensioned assembly plans. They come from the kit manufacturer or the workshop that installs it, and they block more files than anything else. Request them before purchase, not after installation.

What happens to the approval report once the registration certificate is redone?

It is kept with the vehicle and passed on to the buyer in case of resale. It is the one that carries the dimensions of the modified vehicle: the registration certificate takes into account the new approval but does not reprint dimensions, for lack of a box to accommodate them.

Is an old car exempt from the procedure?

No. A wide kit on a 205, an E36 or a Golf 4 is subject to the same individual approval as a kit on an M3 G80. The collector vehicle status is subject to distinct rules, to be checked with the DREAL, and it does not automatically follow from the age of the vehicle.

Does a wheel spacer modify the overall width?

No: a spacer or adapter is placed between the hub and the rim and spaces the wheels, not the bodywork. The issue is different — the wheel must not protrude from the wheel arch, and the spacer must be sized for the offset and the stud length. It is a technical inspection point, not an individual approval.

Does a kit sold as "approved" exempt me from the process?

No, if the kit actually widens the bodywork. The mention refers to the conformity of the part (material, absence of sharp edges, strength), not to the approval of the vehicle that receives it. These are two different levels.

Should I notify my insurer before or after the report?

Before, as soon as the modification is decided or installed. Administrative conformity and insurance coverage are two independent issues: one is settled with the DREAL, the other with your insurer, and waiting for the report to declare leaves a period of uncertainty during which you are driving with a vehicle that your contract no longer describes.

In summary

A wide body kit that actually widens the approved dimensions of your vehicle requires, in the majority of cases, an update of your registration certificate via an individual approval with the DREAL in your region. This procedure, which includes the preparation of a file, a possible technical verification and the issuance of a report, takes time and represents a cost to anticipate from the beginning of your project. Conversely, a classic sport bumper kit that remains within the original dimensions generally does not require this process. In all cases, an initial contact with your DREAL before purchase remains the best way to know exactly where you stand.

Remember the key question that structures this guide from start to finish: does your kit actually change the approved overall width of your vehicle? If the answer is yes, start the RTI process even before purchase, budget the time and cost of the procedure just like the kit itself, and inform your insurer in parallel. If the answer is no, your project remains within the framework of a classic bodywork modification, subject to the usual mounting and safety rules verified at the technical inspection, without additional administrative steps. This simple distinction will save you a lot of complications, whatever the level of ambition of your customization project.

Find our selection of body kits and fender flares by model in our body kit and bumper and fender flares and mudguards collections. To delve deeper into related regulatory topics, also consult our guides fender flares and wheel spacers: the law in France and modifying your grille: law and registration certificate.