In my experience (external contract recruitment) the background check usually happens after an offer has been negotiated and accepted. I've also never seen a background check request for actual salary information. I'm not even sure how that would work... we would just send the candidates' information to this company that churns through court docs to see if they have a criminal history, send them to Quest to get drug tested, donesies bananas. Maybe in the employment verification stage? Even then though, I highly doubt a previous employer would offer that information up - oftentimes they weren't even allowed to comment on the quality of the candidates' work. Nightmare for reference checks to the big EPCs and operators like BP or Jacobs.