I'm having difficulty with separating withdrawals for non-deductible traditional IRAs from withdrawals from withdrawals for 401K rollover IRAs. My non-deductible traditional IRAs were made after tax contributions, so they have a cost basis. My 401K rollover IRAs of course just get treated as ordinary income thus have no cost basis. I'm basically stuck on Form 8606; and I'm not clear how to complete it. The 'step by step' doesn't seem to ask the right questions; and the Form 8606 does not seem clear on this. I have balance at end of 2017 of roughly $66K in non-deductible traditional IRAs and balance at end of 2017 in 401K rollover IRAs of roughly $1,500,000. I've taken withdrawals from both in 2017.