What tax documentation do I need to show a refund of my overcontribution to my 401k?

I had two employers in 2016, and I seem to have overcontributed to my 401k.  My current 401k plan administrator can refund me the overpayment amount, but how do I show this on my 2016 taxes?  Is there some sort of tax document I should be getting from the plan administrator?  Do I get a corrected W-2?