I've never heard of such a thing but it undoubtedly happens. Your pay stub is really just showing the floor though. For many positions, there are fairly regular bonuses, variable comp, etc. So, in reality, there's usually some wiggle room in providing current salary info while still being essentially truthful.
I've been recruiting engineers for almost 20 years, and I have probably had a dozen cases where a client asked for a pay stub around the time an offer is presented. It's obviously rare, and most of the time it was for high-ticket talent that seemed to be paid noticeably above market rate.
I have to say, I find that sorta weird. At that point, I would think if the pay stub didn't square with the claimed salary (and there was no convincing explanation for the difference), they'd almost have to not hire the person. And, if it did square, it's like they'd already decided the price tag was too rich for their blood.
Excellent points, and I'm not necessarily condoning the practice (I don't control that). It does seem they are trying to call a bluff where you either expose the bluffer or get locked in to a rate above market. I can't recall an instance where the stub was provided and the client didn't make a competitive offer, but my data set isn't large.
Maybe it's a "There must be a reason they value them so much" (even though we don't see it) sort of thing. Hardly an uncommon situation. Doesn't mean it worked out in the end :-)
