You’d probably pay a percentage on the gains but you might be able to deduct that from taxable income

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First, even though you missed the tax deduction on the front end, you still should be able to get your IRA contribution to reduce your overall taxable income at tax time. So in the long run, using after tax money shouldn’t hurt you i as you’ll be able to correct this at tax time However, whatever amount of money you transfer from the IRA to the Roth you will have to pay taxes on it.

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So the net effect of your two step process is the same as if you had just put the after tax money into the Roth

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Your financial institution will issue you form 5498 breaking this down. It depends on a few things. Pick either Roth or trad going forward. The pro rata rule is a pain

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