Earlier quoted context omitted.
Not sure why this was downvoted, it's not illegal and companies do it via background checks. Quick searches reveal this is a popular question, spot checks of the answers agree that it's not illegal and quite common.
I think the OP means they can't legally access this information other than by getting you or your previous employer to disclose it. Most large companies won't give out your past salary information, so if they don't force you to provide proof, it's not very likely they will be able to verify it. >via background checks Background checks are normally done via a 3rd party background check company, and they don't have acc…
Yes they do. There's a company owned by Equifax called The Work Number that collects such information.