After-Tax Rollover Cost Basis: When It Changes and When It Doesn’t

Mistake Watch: Indirect rollover pitfalls that trigger tax and penalties

A procedural error on a $150,000 after-tax rollover can trigger immediate tax and penalty consequences. In an indirect rollover, a 20% withholding occurs at distribution, which means $30,000 is withheld from your funds.

To complete a full rollover, you must redeposit the full pre-withholding amount ($150,000) into an eligible destination within 60 days of the distribution date. If you fail to redeposit in time, the $30,000 withheld becomes taxable income in the year of distribution, and, if you are under 59½, a 10% early withdrawal penalty may apply on the taxable amount. For example, at a 24% marginal federal rate and under 59½, the additional tax would be $36,000 and the penalty would be $15,000, totaling $51,000 in taxes and penalties. The actual tax impact depends on your bracket and other income factors.

For a detailed cost-basis illustration in this scenario, see the 401(k) → IRA Rollover Cost Basis: Exact Calculation Steps in 3 Cases and to assess eligibility, consult the Advisor Rollover Suitability Form helps evaluate client rollover needs.

Mechanism: After-tax cost basis behavior across rollover paths

When you move after-tax contributions from a qualified plan to an IRA via a direct rollover, your after-tax cost basis is generally preserved in the new account. The portion that represents your after-tax contributions remains non-taxable on distributions to the extent it equals your cost basis; the earnings on those funds are taxed when you withdraw. If you later convert to a Roth IRA, the IRS pro-rata rule applies: you must allocate taxes across both the basis and earnings proportionally, so a portion of the conversion may be tax-free only to the extent of the basis, with the remainder taxed as ordinary income. To track this correctly, you should preserve Form 8606 records showing your after-tax basis in each rollover and conversion.

To support compliance and documentation, refer to the Plan Rollover Audit Sheet for the required documentation flow, and coordinate timing with the plan using the Employer Plan Exit Timeline.

For compliance workflow and timing, see the Plan Rollover Audit Sheet and the Employer Plan Exit Timeline.

Procedural Steps: Step-by-step path to a cost-basis-preserving rollover

1. Confirm direct rollover eligibility with the current plan to avoid 20% withholding and to streamline the transfer.
2. Initiate a trustee-to-trustee transfer to the designated Traditional IRA custodian and ensure the funds are allocated to the correct cost-basis tracking position.
3. Verify that the after-tax contributions' cost basis is properly documented and transferable; coordinate any required documentation with the plan administrator.
4. If a Roth conversion is contemplated, prepare for the pro-rata allocation and file Form 8606 to report the basis and taxable amount appropriately.
5. After the transfer, confirm the IRA custodian has recorded your cost basis and earnings correctly, maintaining the basis for future tax-free distributions and calculating taxes on earnings when distributed.

Verdict & Open Questions: Concrete path and verification checklist

The direct rollover path to a Traditional IRA is generally the most reliable way to preserve after-tax cost basis and avoid the withholding risk of an indirect rollover. A Roth conversion introduces the pro-rata tax-tracking requirement and may erode some of the tax-free basis if the calculation is not done precisely. Maintain Form 8606 records for all after-tax contributions and ensure ongoing cost-basis tracking in your IRA to prevent future tax ambiguity.

Open questions you must verify next include: Have you confirmed the current plan allows direct rollover to an IRA? Is your after-tax basis clearly documented and transferable? Will you convert to Roth later, and if so, are you prepared for the pro-rata calculation? Review the 60-day window and ensure you have the necessary documentation to complete the transfer without triggering penalties.

FAQ

Does after-tax money get taxed again after rollover?

Not entirely—the after-tax basis is preserved and remains non-taxable on distributions to the extent it equals your cost basis, while the earnings portion is taxed when withdrawn; if you later convert to a Roth, the pro-rata rule applies and taxes are allocated across basis and earnings, so a portion may be tax-free only to the extent of the basis. For example, if you have $40,000 in after-tax contributions (basis) and $60,000 in earnings, a distribution would be tax-free on $40,000 and taxable on $60,000; keep Form 8606 records to track this across rollovers and conversions. You can verify details at the IRS Form 8606 guidance page.

How do I report after-tax basis to IRS?

File Form 8606 with your federal tax return for the year of the rollover or Roth conversion, and maintain ongoing Form 8606 records to reflect your after-tax basis by year and by account if needed; this form tracks your basis and the taxable amounts from conversions, which is essential for the pro-rata rule when you convert to a Roth. For guidance, see the IRS Form 8606 information page.

Can basis be split between accounts?

Yes—in practice you can allocate after-tax basis across multiple accounts and maintain separate basis tracking for each; when you execute future distributions or conversions, you’ll use the respective basis in each account to determine how much is tax-free; if you later do a Roth conversion, the pro-rata calculation will apply across all accounts’ basis and earnings collectively. For example, you might have $25,000 basis in Account A and $15,000 basis in Account B; keep records accordingly and reference the Form 8606 guidance when reporting.

Post-Rollover Maintenance

Final verdict: The most robust path to preserve after-tax cost basis is a direct rollover to a Traditional IRA, which avoids withholding and the 60-day redeposit risk; if you plan a Roth conversion later, you must apply the pro-rata allocation and report it on Form 8606, maintaining ongoing cost-basis tracking to prevent future tax ambiguity. You should implement a disciplined documentation workflow and confirm eligibility with your current plan before initiating the transfer; consult the Plan Rollover Audit Sheet for required documents and timing.

Action steps now: verify direct rollover eligibility with your plan and initiate a trustee-to-trustee transfer to the designated Traditional IRA custodian, ensuring correct cost-basis tracking; confirm the after-tax basis is documented and transferable, and, if you anticipate a Roth conversion, prepare for the pro-rata allocation and file Form 8606 accordingly; after the transfer, ensure the custodian records your basis by account and maintain Form 8606 and related records for future audits. For compliance workflow, review the Plan Rollover Audit Sheet to align timing and documentation: Plan Rollover Audit Sheet.