Two possible places....both in the Federal section of the software
1) For individual US Bonds, Notes that you owned and for Savings Bonds you may have redeemed. The $$ of interest are supposed to go into box 3 of a 1099-INT
2) For US Govt bonds held in Mutual funds, or other bond fund collections, the $$ are included in box 1a on a 1099-DIV form, but that $$ amount will also include dividends from other stocks and bonds.
....2a) When you enter your 1099-DIV form and all it's boxes, there is a follow-up page where you check a box saying "A portion of these dividends is US Government interest" .
...2b) then on a later page you will be able to indicate what sub-$$ amount of box 1a came from US Govt bonds. But, you have to calculate the exact $$ amount from whatever supplemental information the brokerage gives you.
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The $$ entered as I've noted in #1 and #2 above, should transfer and used as deductions in most state's tax returns.
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(Exceptions being CA, CT, &NY ...who place severe restrictions on situation #2 above for 1099-DIV forms...as to whether the US Govt bond $$ can be broken out. No restrictions on box 3 on 1099-INT for individual US bonds one may own)