With regard to regular distributions, including RMDs, all of your traditional IRAs are treated by the tax code as being a single combined IRA. IRA custodians have no way to know your basis in nondeductible traditional IRA contributions, so any regular distribution from a traditional IRA is required to be reported on Form 1099-R with the same taxable amount in box 2a as the gross amount in box 1, with box 2b Taxable amount not determined marked. When you have basis in nondeductible traditional IRA contributions it's your responsibility to file Form 8606 to calculate the taxable and nontaxable portions. TurboTax will prepare Form 8606 for you when you make a distribution and indicate that you have basis in nondeductible traditional IRA contributions. (Because nondeductible traditional IRA contributions are required to be reported when made, if you used TurboTax to file the tax returns for year that you made nondeductible traditional IRA contributions, the basis information should be carried forward automatically when you transfer in the previous year's tax return to begin a new tax return.)
