It's hard to know exactly where you originally entered your Treasury Bill interest.
IF....(big IF)...IF on your original tax return...if you properly entered the Treasury Bill interest in BOX 3 of a 1099-INT form (not in box 1), then that amount would automatically be subtracted from ID income somewhere on the ID tax forms.
Don't try to change it in the ID forms themselves....only make sure the $$ are entered only in the federal area ...again, box 3 of a 1099-INT. Changing it in the Federal area wouldn't change the federal taxes owed, since box 1 and box 3 $$ of the 1099-INT are taxed the same by the Feds,
And any $$ in box 3 of that 1099-INT Federal form, should automatically show up on line B.3. of the Idaho form 39R.
____________*Answers are correct to the best of my knowledge when posted, but should not be considered to be legal or official tax advice.*
