I have a calendar 401k plan where an ADP refund for 2005 plan year was processed before March 15, 2006 where 10% was withheld for Fed Taxes. Particpant has a 2006 1099-R coded 'P'. Question - regarding the fed tax withheld - would the participant report this in his 2005 personal return or his 2006 return? The refund is includible in his 2005 income, but I'm not sure about the tax w/h and I can't find a definitive answer.

Mahalo!

I'd say the code P applies to everything reported on that specific 1099-R, which means both the distribution and the withholding. I'd put them both on the same year.