Beyond the contribution and conversion themselves, one real, IRS-required step is commonly overlooked: filing Form 8606 with your tax return for the year you make a nondeductible Traditional IRA contribution, and again in the year you convert.

Form 8606 documents your “basis,” the after-tax dollars you’ve already contributed, so the IRS doesn’t tax that portion again upon conversion or eventual withdrawal. Failing to file it means you lose the paper trail proving those dollars were already taxed, a real, documented risk of being taxed twice on the same money down the line.

The IRS’s own Form 8606 instructions (available at irs.gov) walk through exactly how to calculate your basis and the taxable portion of any conversion; keeping copies of every year’s Form 8606 is a real, practical safeguard tax professionals commonly recommend.