Apparently they've started asking for proof recently 2 years ago I changed mine from 1.3 to 3.0 from just filling in the v5, changed my mrs' Ka from 1.3 to 1.6 recently and they wanted a receipt of purchase, engine number and a letter from a garage/RAC to confirm that engine is in there, no one would say they have a bigger engine (and pay more tax) if they didn't have one so I don't see the point, billy bullshitter would have to reach an all time low to prove to his mates he has a 15 litre engine in his corsa lol