There was a fun Quora post not too long ago about someone asking "I made up a number, now they want proof as part of a background check, what do I do?" My own strategy I intend to apply in the future is to give my base salary + bonuses etc. If they never clarify I can only assume they had meant total compensation, not base, and who am I to complain if they offer me my current total as my new base?
I did the same. Every time I moved jobs I got a pay raise because the number I provided was above what I was currently making. In a few cases, they offered well above what "I wish I had," which was a nice bonus.
I had a company I was talking to ask, and say up front that they would need pay stubs as proof.
Some companies will ask you to sign their contracts in blood if they thought they could get away with it. Doesn't mean that you should.
And that's why it was a company I was talking to, and not a company that I worked for. But, I recognize that I was in a fortunate position, and I did not currently need a job then. Had I been in a less fortunate position, things could be different.