Do you want to make technical modifications to your vehicle or trailer? This may invalidate your operating license. You must prove that the technical modifications comply with the regulations. The registration authority can then issue you with a new operating license for the vehicle.

Before installing or converting the vehicle, find out whether

• the operating license will be affected or
• the modification can be approved at all and you can obtain a positive expert opinion for a new operating license.

Contact officially recognized experts for motor vehicle traffic or a technical service designated for the approval of complete vehicles with these questions.

Certain technical modifications that lead to the expiry of the type approval must be assessed by an officially recognized expert from the technical inspection authority for motor vehicle traffic or a technical service designated for the approval of complete vehicles. Modifications that require approval in accordance with Section 19 (3) StVZO can also be approved by a test engineer from an officially recognized vehicle inspection organization (e.g. TÜV-SÜD, TÜV Rheinland, TÜV Nord, TÜV Hessen, TÜV Thüringen DEKRA, GTÜ, KÜS, FSP). You must then notify the registration authority of certain changes as soon as possible. These include, for example

• Changes to the vehicle class or the vehicle and body type
• Changes to engine capacity, rated power, fuel type or energy source
• Increase in the maximum design speed
• Reduction of the maximum design speed if this is relevant to the driving license or registration
• Modification of the permissible axle loads, the total mass, the drawbar load or trailer load
• Increase in vehicle dimensions, except for passenger cars and motorcycles
• Changes to the number of seats or standing room in buses and coaches
• Deterioration of exhaust or noise values or changes insofar as they have an effect on vehicle tax or traffic bans.

The prerequisites for incorporating the technical modifications into the vehicle documents are:

• You must prove that the modifications have been made in accordance with the regulations. To do this, you must have the vehicle inspected by officially recognized experts for motor vehicle traffic. If you can prove that the vehicle complies with regulations by means of a general operating permit (ABE) for vehicle parts or a parts certificate, you will need an acceptance certificate. This does not apply to vehicle parts for which the ABE does not stipulate an acceptance requirement.
• If someone is to represent you when applying for the modification, you must give this person written authorization. Your representative must present the power of attorney and provide proof of identity.
• In the case of several modifications that may affect each other (e.g. modification of the wheel/tyre combination and subsequent lowering), a combined assessment may be required.

You or your representative must report the technical changes to the responsible registration authority by presenting the registration certificate and, if necessary, apply for a new operating permit.

Depending on the services offered by your registration authority, a form is available for you to download. You can find information about the registration authorities under "Further links".

The registration authority may require you to present the vehicle.

The deadlines in the expert report must be observed.

• The following documents are required:
  
  • valid identity card or passport with confirmation of registration
  • In case of representation: additionally
    • written power of attorney
    • valid identity card or passport of the authorized person
  • for minors: additional declaration of consent and identification documents of the legal guardian
  • for legal entities/companies:
    • Extract from the commercial register or
    • business registration or
    • extract from the register of associations
  • Registration certificate part I or old vehicle registration document
  • Registration certificate part II or old vehicle registration document
  • Expert report or operating license from the parts manufacturer
  • Acceptance certificate from an approved testing organization (e.g. TÜV-SÜD, TÜV-Nord, TÜV-Rheinland, TÜV Hessen, TÜV Thüringen, DEKRA, GTÜ, KÜS, FSP)
  • Proof of a valid general inspection (HU) by means of the last HU report or the entry in the registration certificate part I
  • if the emission class has been changed by installing a catalytic converter (KAT) or an exhaust gas purification system or diesel particulate filter:
    • Installation certificate from a recognized AU workshop
    • Type approval (ABE) for the installed exhaust gas purification system

The fee depends on the administrative costs (from EUR 11.40).

If you are still in possession of a vehicle registration document and vehicle registration certificate that were issued before 01.10.2005, it is necessary to exchange them for new vehicle documents (registration certificate part I and part II). The costs for the exchange are borne by the vehicle owner.