You are correct. Ultimately you need to have the discount amount taxed at the federal level but identified as US Treasury interest so that your state subtracts it from state taxable income. You have two options.
1. If you already have a form 1099-INT entered in TurboTax with box 1 interest (at least equal to the market discount amount), simply move an amount equal to the market discount you entered in the bond sale topic from box 1 to box 3 in the 1099-Int topic. This keeps the total interest the same on your federal return but identifies the correct amount as US Treasury interest to flow to the state return.
2. If you do not already have box 1 1099-Int entered (or not enough to cover the market discount) then do not enter the market discount in box 1f for the bond sale. Instead create a 1099-Int entry for the brokerage and enter the market discount amount in box 3 using the 1099-INT topic. That interest will then be properly taxed at the federal level but carry to your state return as a subtraction.
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