Telling your insurer after a remap: why and how

Why does the law make you tell your insurer?

Insurance works on one premise: the company sets the price based on what it knows about the risk. If the risk changes and the insurer doesn't know, the contract is no longer balanced. Spain's Insurance Contract Act, Ley 50/1980 de Contrato de Seguro, deals with this in three articles worth knowing:

Article 11 doesn't mention ECU remapping, of course. It talks about circumstances which, had the insurer known about them when the policy was taken out, would have led it not to insure you or to do so on more expensive terms. An engine modified to deliver more power fits that description quite easily. Many policies also ask specifically about vehicle modifications in the initial questionnaire.

What happens if you tell them?

This part is governed by article 12, and it sets specific time limits:

In practice, one of three things usually happens: the insurer notes it with no changes, it adjusts the premium, or it tells you it doesn't insure modified vehicles. Any of the three leaves you with a clear position. If you end up without cover, at least you know in time to find another insurer that will cover it.

And if you don't tell them and you have an accident?

The same article 12 covers this case, and it's the one that should worry you most:

• Without bad faith: the insurer reduces what it pays you in proportion to the difference between the premium you were paying and the one it would have charged had it known the real risk.
• With bad faith: the insurer is released from paying.

Where is the line on bad faith? That is for the insurer and, if it gets that far, a judge to decide, case by case. Having hidden something the policy asked about specifically won't help. Nor will the modification being directly related to the claim.

Remember that the other half of the equation is the ITV (Spain's compulsory periodic vehicle inspection, similar to the UK MOT) and the Traffic Act: if the remap changes the power output and it hasn't been processed as a vehicle modification (reforma) that must be legalised, the vehicle is being driven with an unauthorised modification (article 12.7 of Real Decreto Legislativo 6/2015, Spain's Traffic Act). That can also come up when a claim is assessed. We explain it in remapping and passing the ITV.

How do you notify them, step by step?

You don't need a lawyer. You need to be organised and have a dated piece of paper.

1. Find your policy and the questionnaire

   check whether you were asked about vehicle modifications and what the general terms and conditions say about an increase in risk.

2. Gather what was done

   the invoice for the work, which should describe what was done, and a simple description of what was changed. If we carry out the remap, the invoice describes the work and we also give you a document setting out the work carried out, designed precisely for cases like this. You don't need technical detail: "remap of the engine ECU, no parts changed, emissions control systems unmodified".

3. Write to the insurer

   by email, through the online customer area or by letter. Identify the policy and the vehicle, and explain the modification and the date it was carried out.

4. Ask for a written reply

   for confirmation of whether your cover stays the same, whether the premium changes or whether they can't insure it.

5. Keep everything together

   your notification, the acknowledgement and the reply, along with the invoice for the work.

Here's an example of what you could write, so you get an idea of the tone:

Adapt it to your situation. If the work included parts (a Stage 2, for example), say so as well.

What mistakes should you avoid?

• Only telling them by phone. The day you need to prove it, there will be no record.
• Giving a half description. "A tune-up" is not an ECU remap. If the insurer later finds out something else, your notification won't be much use to you.
• Assuming every insurer covers it the same way. Each company has its own policy. Ask before remapping if you want to avoid surprises.
• Forgetting to report the change back. If you return the car to stock software, say so too. Article 13 lets you ask for the reduction in risk to be taken into account.

What should you ask your insurer before remapping?

If you haven't remapped yet, you have an advantage: you can ask before you decide. These questions usually clear things up in a single call or email:

• Does my policy say anything about modifications to the vehicle or the engine? In which section?
• Do you insure vehicles with a remapped engine ECU, with no parts changed?
• If I notify you, what documents do you need? Is the invoice enough?
• Does any specific cover change, such as own damage, theft or roadside assistance?
• If I later put the car back to standard, how do I notify you?

Ask for the answer in writing. If the insurer tells you it doesn't insure modified vehicles, at least you know before spending anything, and you can compare other insurers or decide not to remap.

When is it better to think about not remapping?

There are situations where we'd tell you to think twice:

• If your insurer doesn't cover modified vehicles and you have no reasonable alternative.
• If it's a company car or a leased car, because you are not the registered keeper or the policyholder, and the decision isn't yours alone.
• If you aren't prepared to tell your insurer. Then you carry the whole risk yourself.

None of these is a technical bar: the engine may be perfect for a Stage 1. They are paperwork decisions, and it's best to make them beforehand.

The practical summary

Before remapping, call or write to your insurer and ask how it treats engine modifications. Afterwards, notify it in writing with the invoice. Keep the reply. It's twenty minutes that can save you a very expensive headache. You'll find the rest of the rules that affect an ECU remap in legality, ITV and insurance.

Reviewed on 15 October 2026.