Traditional IRA basis is generally the cumulative nondeductible contribution amount that has not already been recovered tax free, not the account’s market value. If Form 8606 line 2 mistakenly used the full IRA balance, rebuild every nondeductible contribution and distribution, correct the earliest wrong form, and carry the corrected line 14 through later years.
An April 2026 tax thread described entering a $23,000 IRA balance as basis and carrying that error through later contributions and a rollover. The mistake can make conversions look less taxable than they are.
Start here: a practical action plan
- Open the official source and confirm the rule for your coverage, tax year, filing status, and deadline.
- Collect the notices, statements, plan documents, forms, and dated confirmations that control the decision.
- Replace the hypothetical figures with your actual amounts and keep the checked calculation with your records.
- Record the next deadline and obtain written confirmation after an enrollment, correction, appeal, or payment posts.
- Treating a forum answer, portal label, or plan summary as the final authority for a coverage or tax result.
- Comparing amounts on different tax, timing, or coverage bases without converting them to the same basis first.
- Discarding dated evidence that may be needed for an enrollment, appeal, tax correction, or claim dispute.
Separate basis from account value
Basis comes from nondeductible traditional IRA contributions and certain other nontaxable amounts. Investment growth, deductible contributions, and pretax rollovers are not basis. Form 8606 line 2 generally comes from the remaining basis on the last applicable Form 8606, not a brokerage statement’s ending value.
Collect every Form 8606, Form 5498, Form 1099-R, IRA statement, and tax-return IRA deduction. Mark each contribution as deductible, nondeductible, or excess. A contribution is not nondeductible merely because cash came from an after-tax bank account.
Correct the first wrong year before later years
Find the first Form 8606 where beginning basis does not match the prior form’s ending basis after valid adjustments. Recalculate that year using the proper year-end value, distributions, conversions, and contribution timing. Then carry the corrected result into each later year.
Submitting only the newest corrected form can leave the IRS record inconsistent with prior conversions or distributions. Use the prior-year forms and instructions for each affected year. Determine whether amended income-tax returns are needed because taxable IRA income, additional tax, credits, or deductions changed.
Worked example: $23,000 of value is not $23,000 of basis
Example: an IRA is worth $23,000, but records show only a $1,000 nondeductible contribution and no prior basis. The taxpayer mistakenly enters $23,000 on Form 8606 line 2, then adds $7,000 of nondeductible contributions in each of two later years.
Ignoring distributions for illustration, claimed basis becomes $37,000, while supported basis is $15,000. The overstatement is $22,000. A later $8,000 conversion could be reported far too tax free if the incorrect $37,000 basis is used. The official pro-rata worksheet must use all traditional, SEP, and SIMPLE IRA balances.
| Basis component | Claimed | Supported |
|---|---|---|
| Opening amount | $23,000 | $1,000 |
| Later nondeductible deposits | $14,000 | $14,000 |
| Total before distributions | $37,000 | $15,000 |
| Overstatement | $22,000 | $0 |
Review rollovers and conversions after correcting basis
Pretax money can generally move from an IRA to an eligible employer plan, but after-tax IRA basis generally cannot be rolled into the plan. An overstated Form 8606 does not transform pretax value into basis, and a plan administrator’s transaction record does not correct the tax return.
Reconcile any reverse rollover, Roth conversion, and year-end IRA balance against the corrected basis. Keep a permanent basis file after the amendments are accepted. Form 8606 protects against double taxation only when the contribution history and distribution calculations are accurate.
- Inventory every contribution and deduction.
- Find the earliest incorrect basis year.
- Recalculate all later Forms 8606 in sequence.
- Review conversions and plan rollovers for tax changes.
Frequently asked questions
Is my traditional IRA balance the same as basis?
No. Basis generally represents unrecovered nondeductible contributions, not market value or investment growth.
Where does Form 8606 line 2 usually come from?
It generally comes from the remaining basis on the last applicable Form 8606, adjusted for specified events.
Should I correct only the newest Form 8606?
Usually no. Correct the earliest error and carry the corrected result through every later affected year.
Does an after-tax bank transfer automatically create IRA basis?
No. The tax return must classify the contribution as nondeductible, and deduction eligibility and reporting matter.
Can IRA basis be rolled into a 401(k)?
Eligible plans generally accept the pretax portion of an IRA rollover, not the after-tax basis portion.
Why does an overstated basis matter?
It can understate taxable income from conversions and distributions, producing incorrect returns and notices later.
Sources and review notes
The calculations and scenarios in this guide are original BreadWinnr worked examples. We recalculated each example and checked that its parts match the stated total. Official sources support the financial concepts. Forum links document the reader problem that prompted the guide and are not treated as financial authority.
Read our research, testing, corrections, and source policy.
This guide provides general financial education. It does not account for your complete financial, tax, legal, or contractual situation.
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