I had to do this for an interview last week. It was a Skype interview with a guy overseas I had met at a trade show. His company's booth was next to mine, so we spent many hours chatting over those few days together. And he saw me in action and knew pretty well what I do. When the Skype interview began, he came right out and said they had planned to contact me after the show, but that I had gotten to them first (three weeks later). He said his only question was whether he could afford me. So I told him what I was getting and would likely earn if I stayed put. He later sent me a thank you email (before I could send him one) and asked me to write it all out for him. I don't think he's going to ask for a W2 and I based what I need from them on what I am pretty sure I'll make by staying put.

That's bulls**t.... I just accepted a new position and that question never came up until a formal offer was on the table. I was asked my prior salary once a verbal offer was given and only provided proof AFTER I signed the formal offer.