Why it counts as a modification
Insurance is priced on the vehicle as declared. A change to engine management software changes how the vehicle performs compared with the manufacturer specification, so insurers generally expect to be told.
What to tell your insurer
Be specific: that the engine management software has been remapped, when, and by whom. If the insurer asks for details of what was changed, we can describe the work carried out on your vehicle.
Why declaring it matters
An undeclared modification can affect a claim or the validity of a policy. That is a far bigger financial risk than any premium difference.
Some insurers are comfortable with a software remap, some adjust the premium, and some decline. It is worth asking before the work rather than after.
Leased, financed and company vehicles
If a vehicle is leased, financed or company-owned, the agreement may restrict modifications. Check the terms and obtain permission first.