If you have a basis, IRS asks (insists) that you keep ALL form 8606 that you filed, forever, along with the 1040 to show you did not take a deduction for your contribution shown on Form 8606.
IRS says:
"All distributions from your IRA will be taxed unless you can show, with satisfactory
evidence, that nondeductible contributions were made."
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For purposes of recovery of state taxes on IRA distributions, you need complete records of all contributions and distributions so far.
