If I take a 401k distribution in January 2010 can I claim it as income on my 2009 tax return?

Income received in January 2010 is 2010 income. However, if the distribution check is actually dated 2009, I think you can argue it's 2009 income even if you didn't receive it in the mail until 2010.

If the 401k administrator report this as 2009 withdrawal, then you report on 2009 tax return. Else on 2010 tax return.

If the 401k administrator report this as 2009 withdrawal, then you report on 2009 tax return. Else on 2010 tax return.

Good point - if this is a 2009 withdrawal you should receive a 1099-R from the administrator for tax year 2009.