Catching up on basis
If you made nondeductible IRA contributions in prior years but never filed Form 8606, file the missing returns now to establish your basis. Without 8606 records, the IRS will treat all subsequent IRA distributions as fully taxable, costing you tax on after-tax dollars.
Statute of limitations
Form 8606 is a basis-tracking form, not an income-reporting form, so the normal three-year statute of limitations does not bar a late filing. You can file Form 8606 for years going back as far as needed, although gathering supporting records (IRA statements showing contributions) becomes harder over time.
How to file
Each missing year requires its own Form 8606, filed standalone with the $50 late-filing penalty (which is often waived for reasonable cause). Mail to the same address as the corresponding Form 1040.
Document with care
Attach a statement explaining why prior years were missed and include copies of IRA statements showing the contributions. The IRS often waives the $50 penalty when the taxpayer initiates the catch-up filing and the records support the basis claimed.
When it really matters
Late 8606 filing is most valuable for taxpayers approaching retirement who have decades of nondeductible contributions never tracked. Establishing basis can save thousands in tax over the distribution period.
Where the numbers actually flow
Every dollar that touches Filing Form 8606 for Prior Years has a downstream destination — usually a line on Form 1040, a schedule that feeds Form 1040, or another supporting form. Tracing the flow once, with last year's return open in front of you, makes the form intuitive in a way that reading the instructions cold rarely does. The high-leverage takeaway is that small-business returns are interconnected: a change on one form ripples through three or four others, and a software package or preparer that does not recompute every dependent line on every change can produce silently incorrect results.
Software vs. paper filing
Most filers use commercial tax software or a tax preparer to handle Filing Form 8606 for Prior Years — and that is the right call for nearly all small-business returns. The IRS Free File program is open to taxpayers below an annually adjusted income limit and supports most small-business forms. Direct paper filing is technically still an option but is slower, more error-prone, and increasingly relegated to corner-case situations. Whichever path you choose, retain a digital PDF of the as-filed return for at least three years (six if you under-reported income by more than 25%).