Document (1): report from an approved technical service on the compliance of the modifications with the legal framework (individual approval).
Document (2): conversion certificate from an automotive professional with the chassis number, a precise description of the modifications and references to the technical reports (TÜV, Gutachten) of the parts, plus copies of those reports.
Equipment or accessories that stick out beyond the front or rear of the vehicle are regulated separately in the Arrêté grand-ducal of 23 November 1955; a side projection of more than 0.20 m must be signalled.
A combination of modifications that influence each other (for example wheels and suspension, spacers and suspension, power and wheels) always needs document (1).
The check must happen before the vehicle goes back on the road, or at the latest before the next technical inspection and never more than 2 months after the modification.
If the change is not entered in the 'remarques' field of the registration certificate, the inspection records a major defect.
If the documents are incomplete, the vehicle must go to an approved technical service for a compliance report.