IMO it depends on where you are trading it in and at what budget level.
If you are taking it into a main dealer, they'll use it as a tool to knock you down on price then pitch it as a positive to the next buyer (enthusiast previous owner blah blah blah). Just the way of the world, particularly at the moment where demand is greater than supply.
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^^^^^^ This is exactly my findings as well.

You turn up to PX a car, armed with carefully documented service history and all receipts/mot paperwork to go with it and your paperwork is dismissed as worthless as you’ve serviced it yourself, albeit every five thousand miles.
The last time I did that I was told that they didn’t want to accept a customers service history paperwork due to covid, even though a garage will still give you a receipt with a breakdown of what’s been done, which is still paperwork that I would leave in the car for the new owner.

As said, when they get to a certain age and budget, I really don’t think servicing it yourself matters that much as the overall condition of the vehicle is then taken in to account, along with your own documentation of the service history. My full service history is online only but I daresay that dealers can fill in any gaps for vehicles that aren’t up to date. Would they dare to do such a thing ……. hmmm.
