Cabinet Codifies Portugal's Vehicle Modification Rulebook in a Standalone Decree-Law — IMT Authorisation, Homologated Parts and Emission Caps Replace the Old Technical Circular Stack

The Portuguese Conselho de Ministros (Council of Ministers) on 18 June 2026 approved the Regulamento das Transformações de Veículos (Vehicle Transformation Regulation), a standalone Decreto-Lei (Decree-Law) that pulls the rulebook for modifying any registered Portuguese vehicle into a single legal text. Until now the modification regime sat across dozens of technical circulars issued by the Instituto da Mobilidade e dos Transportes (IMT, Institute for Mobility and Transport), each amended piecemeal since the 2010 framework first took shape. The result was a workshop-by-workshop interpretation problem that left modifications routinely accepted at one IMT counter and rejected at another.

Three principles, one rulebook

Three operating principles anchor the new text. First, any transformation that touches a vehicle's regulatory characteristics — engine, gearbox, axles, suspension geometry, fuel system, identification plate or category classification — requires prior authorisation from IMT before the work begins. Engineers must file a technical dossier signed by a certified inspector; retrospective legalisation is no longer available once the change is on the road. Second, any installed component must carry European homologation certification — non-homologated aftermarket parts cannot be retrofitted to a registered vehicle, full stop. Third, the modified vehicle must clear the same emissions ceiling as its original category at the next centro de inspeção (inspection centre) visit, and IMT can order an extraordinary inspection at any time within 24 months of registering the change.

The combustion-to-electric retrofit opens

The single biggest opening the decree creates is the legal channel for retrofitting petrol or diesel cars to electric drive. Conversion specialists in Aveiro and Águeda have told Lusa that the previous regime forced retrofit clients to register the modified vehicle as a new construction, a process that took 8-14 months and reset the vehicle's identification plate. Under the new text the retrofitted vehicle keeps its matrícula (number plate), its IUC (Imposto Único de Circulação, vehicle circulation tax) banding and its insurance history; only the energy classification is overwritten. That removes the single biggest cost barrier in a market that the European Commission estimates could absorb 40,000 retrofitted vehicles per year across the Iberian peninsula by 2030.

What this means for expat car owners

• Imported vehicles: If you brought a vehicle in under the matrícula transposition route through customs (Direção-Geral das Alfândegas), the decree clarifies that any modification carried out abroad before importation is treated as part of the original specification — provided the foreign workshop's invoices and homologation references travel with the customs file. That ends a long-standing double-counting trap where an aftermarket suspension on a UK-imported Land Rover or a German-fitted LPG kit triggered a separate Portuguese homologation requirement on top of the import process, adding €600-€1,800 to the legalisation bill.
• Older retrofit jobs: Vehicles modified before the decree's entry into force are not retroactively unwound, but any modification recorded after the entry-into-force date must follow the new authorisation track. A six-month transition window covers dossiers already submitted to IMT under the old circulars.
• Insurance implications: Multi-risco motor insurers have signalled they will tighten declaration requirements on modified vehicles. Failure to declare a homologation-affecting modification can void the policy at claim time — the new decree does not change that risk, it just makes the underlying compliance test clearer.
• Inspection cycle: The extraordinary-inspection power within 24 months means a modified vehicle can be summoned outside its normal inspection schedule. Keep the IMT authorisation paperwork in the vehicle.

The decree-law is expected to be published in the Diário da República (Official Gazette) within ten working days and enters into force 30 days after publication. IMT director João Marrana told a Friday briefing that the technical circular stack will be formally revoked on the same day, with a six-month transition window for vehicles already in modification dossiers. AICA (Associação Industrial Portuguesa de Construtores Automóveis) backed the text on Thursday, framing it as a precondition for the retrofit conversion market to scale into a genuine industrial segment rather than a niche workshop trade.