...hard to know without details about exactly where every source income came from.....especially if it was a mix.
For instance, if virtually all of it was from Qualified dividends, and long term capital gains...the tax rate could be 0%. But once Interest and Retirement income get mixed in...not sure how it is figured as the tax tables are not used in either situation.
Probably there are details on a worksheet called Qualified Dividends & Capital Gain Tax Worksheet.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*