I was working for a (10-year-old) start-up in the Netherlands, that fired me after one year of employment, because the owner's friend, who was suddenly appointed as an executive, decided he didn't like my face.
Fast forward 18 months later, I am contacted by someone working for my ex-employer, asking me to sign timesheets for some of the months I was employed with them. They submit these timesheets to the Dutch government to receive tax deductions related to R&D work. Whether or not they modify this data to achieve favourable tax benefits is another discussion.
I have copies of the aforementioned timesheets that I signed shortly before the last time I left the building. It's not my responsibility to check these things.
My reply to them: €100 per signature. They never accepted this but in the end they probably just forged my signature.
Moral of the story is – you NEVER owe your former employers anything!