How do I calculate the amount of interest from US Government obligations in an IRA, if some of the interest was earned in an earlier year than the IRA distribution?

[MarkHA]

On my state tax return, can I deduct all of the interest that hasn't already been deducted, or do I need to come up with some kind of ratio?

[DavidD66]

No you can't deduct all the interest that hasn't been deducted.  If you had $100,000 in your IRA on December 31, and that balance included $5,000 of interest from US Government Obligations, then your distribution would include 5% US Government Interest.   If your state allows for a deduction of the interest on the prorated portion of interest from US Government obligations, you would have to have been tracking the amount earned each year.  Otherwise you would need to go back to your year-end statements to get the amounts.