Any basis in an IRA is contribution or conversion basis, not capital basis. Capital cost basis only applies to capital investments outside of an IRA or qualified retirement plan. Any taxable amount distributed from an IRA is taxed as ordinary income.
Forms 1099-R for regular distributions from a traditional IRA (code 1, 2 or 7 by itself) are required to have the same amount in box 2a as is in box 1 and to have box 2b Taxable amount not determined marked. The entire amount is taxable unless the IRA has basis in nondeductible traditional IRA contributions. If your ex-husband's IRA had basis in nondeductible traditional IRA contributions, half of that would have transferred to you with the half of the IRA that transferred to you. You would need to get the basis information from Form 8606 filed with your previously filed joint tax return.
Forms 1099-R for regular distributions from a Roth IRA (code J, T or Q by itself) are required to have box 2a blank and box 2b Taxable amount not determined marked. If it's code J, you'll need to enter into TurboTax your basis in Roth IRA contributions and conversions. As with a traditional IRA, half of the basis in Roth IRA contributions and conversions would have transferred to you with the transfer of half of a Roth IRA.
