A classic car that's been modified from its original factory specification, even a change that feels minor to the owner, sits in a different risk and cover category to a fully original example. Getting this wrong is one of the most common ways owners unintentionally invalidate a claim.
What actually counts as a modification
Modifications aren't limited to obvious performance upgrades. Insurers typically want to know about:
- Engine changes, including re-mapping, different carburettors, or a swapped engine
- Suspension, brakes, and wheel changes from original specification
- Bodywork alterations, including non-standard paint schemes in some cases
- Interior changes such as non-original seats or a modern stereo system, depending on the insurer
- Exhaust systems that differ from factory specification
When in doubt, declare it. Undeclared modifications are one of the most common reasons classic car claims get disputed or reduced, even when the modification itself had nothing to do with the incident being claimed for.
Why this matters for agreed value too
Modifications can affect a car's agreed value in either direction. Period-correct upgrades or manufacturer-endorsed modifications can sometimes add value for certain collector markets, while non-period modifications can reduce it, or require separate specification and cover for the modified parts themselves.
Insurers that specifically cater to modified classics
Some specialists price modified classic and performance vehicles more confidently than others, since it's a larger part of their core book rather than an exception they handle cautiously. It's worth asking directly how comfortable a given insurer is with your specific modifications, rather than assuming any classic specialist will treat modified and original cars identically.
What to have ready when declaring modifications
- A full, honest list of everything changed from factory specification
- Receipts or documentation for significant modifications where available
- Photographs of the current specification, particularly for anything visually different from standard
- Details of who carried out the work, particularly for engine or safety-critical modifications
Not sure where your own cover stands?
A private review takes one conversation and costs nothing.
Request Information →Frequently Asked
Will modifications automatically void my classic car insurance?
Not automatically, but undeclared modifications can lead to a claim being disputed or reduced. The key requirement is declaring modifications honestly when you take out the policy.
What counts as a modification for classic car insurance purposes?
Engine changes, suspension and brake upgrades, non-standard wheels, bodywork alterations, and even some interior changes can all count, depending on the insurer's specific criteria.
Do modifications always increase classic car insurance premiums?
Not always. Some period-correct or manufacturer-endorsed modifications may have limited impact, while significant performance modifications typically increase premiums.
Should I get my modified classic car separately valued?
It's worth it. Modifications can affect a car's agreed value in either direction, so an up-to-date valuation reflecting the current specification helps avoid disputes later.
Are some insurers better suited to modified classic cars than others?
Yes. Some specialists deal with modified and performance classics as a core part of their business, and tend to be more comfortable pricing and covering them than insurers who mainly handle original, unmodified vehicles.