What alterations can result in the permit for use (Betriebserlaubnis) being cancelled?

The permit for use (Betriebserlaubnis) can be cancelled if you make a modification that changes the vehicle in a way that is no longer covered by its type approval, or if road safety or environmental requirements might be affected.

Answer 1 (fitting a sidecar) is a classic case: adding a sidecar fundamentally changes the vehicle type, its dimensions, weight distribution, handling, and braking behavior. That’s not a minor accessory; it’s a major structural/technical change. Without an official approval/inspection and the proper entry in the papers, the vehicle is no longer considered approved in its modified form.

Answer 2 (fitting tyres of a different size) can also cancel the Betriebserlaubnis because tyre size directly affects speedometer accuracy, ground clearance, gearing, braking and stability systems, and whether tyres can rub on the bodywork. In Germany you must use only the tyre sizes that are approved for your vehicle (listed in the vehicle documents/CoC or covered by an ABE/parts certificate). If you fit a size that isn’t approved and don’t have it legally accepted, you risk losing the Betriebserlaubnis.

Answer 3 (fitting a rear fog lamp) usually does not cancel the permit as long as it’s installed correctly and meets the legal requirements (approved lamp, correct positioning, proper switching/tell-tale, not dazzling). It’s typically considered an allowed equipment addition rather than a change that alters the vehicle’s essential characteristics.

Rule of thumb for similar questions: changes to core technical characteristics (structure, wheels/tyres, suspension, engine, steering, braking) are the ones most likely to void the Betriebserlaubnis unless they have an approval and, where required, an inspection and registration. Adding compliant lighting equipment is often allowed if it’s E-approved and installed per the rules.