Pretty sure they use invoice price.
Then, if you get the vehicle replacement plus and wrote the car off, they'd pay the difference between invoice and on the road (or whatever negotiated price for a replacement).
If you try and claim OTR price for their normal return to invoice cover, could that not potentially be classed as fraud?
I thought the whole point of vehicle replacement plus was they made up the difference for you to buy exactly the same vehicle.
Say you have bought a VW recently with the £1000 loyalty and £1250 pcp contribution that put the price of the car down to £24,000. If you put that as the vehicle price value for GAP and your car gets stole and those financial contributions have stopped then you would effectively still be out of pocket by £2250 plus any discount you had received.
Would they not be at liberty to say to you "Well £24,000 is what you told us the car costs to replace"
The more you put as an invoice price the more the cover costs so you are actually paying for it.
Taking it to the extreme, imagine you had bought a car at half price because you were the 100,000th customer!!
As far as I know they just pay you by cheque for the difference so you can go and get any car you want. They don't actually "wait for a negotiated price"
If I was still going to be out by a few thousand, Then I wouldn't see the point of GAP.
EDIT: I've just had a look at ALA and it does seem quite confusing. On the first page of finding out more
https://www.ala.co.uk/gap-insurance it asks for an On The Road price.
Then if you click quote me and select "Vehicle Replacement Plus"
https://www.ala.co.uk/quote.php?action=goto&prod=GAP&group=cars&options=1&qual_gap=1 It states "Full list price of car: The price of your vehicle before deducting any discounts."
I still definitely wouldn't go with the price I paid.