Timing · 2025 and 2026

The December 31 IRA Balance Rule and Timing Trap

Published by Moss Ladder · Updated October 17, 2026 · Editorial policy

Executive summary

An early conversion does not freeze the year's pro-rata result. Form 8606 generally combines the owner's relevant annual distributions and conversions with the applicable December 31 IRA snapshot. An incoming rollover months after a conversion can therefore change the allocation. Plan around the entire calendar year and keep evidence of what actually remained at year end.

Educational guidance for ordinary scenarios. Check the official form's year and filing branches and obtain advice for your actual records.

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Why the transaction-date balance is not enough

Suppose an owner makes a nondeductible contribution and converts it in January, when a newly opened traditional IRA has no other assets. It is tempting to conclude that the transaction is permanently clean because the account was empty immediately afterward. The annual Form 8606 calculation does not stop with that account's January statement. IRC § 408(d)(2) and the form's line 6 instructions generally bring in the owner's applicable traditional IRA balances at the end of the conversion year.

Inventory all owned traditional, traditional SEP and traditional SIMPLE IRAs, including rollover accounts at other custodians. A zero statement at the brokerage used for the conversion does not exclude value held elsewhere. Do not combine a spouse's separately owned IRAs with yours, and do not add a qualified employer-plan account that remains in the plan. If assets leave that plan and arrive in an IRA before year end, however, their classification and effect can change. The account destination matters more than the timing of the original conversion request.

A later job-change rollover can change an earlier conversion

Assume $7,000 available basis and a $7,000 conversion early in the year, with no other relevant distribution. If the owner has no applicable IRA value at December 31, the ordinary model allocates all $7,000 basis to that conversion. Now suppose a November job change leads to a $63,000 pre-tax 401(k)-to-IRA rollover, and that money remains in a traditional rollover IRA at year end. The annual denominator is $70,000, not the $7,000 seen in January.

The tax-free ratio becomes $7,000 divided by $70,000, or 10%. Only $700 of the conversion is tax free, while $6,300 is taxable and $6,300 basis remains for later use. The incoming rollover itself is not being treated as a Roth conversion in this example; its effect comes through the IRA year-end value. Keeping the old employer plan, moving to another eligible employer plan, or using a valid later IRA-to-plan rollover can describe different facts. Availability and suitability must be checked separately.

January conversion followed by a $63,000 incoming rollover

This invented example assumes one taxpayer, documented basis, eligible ordinary transactions, no special repayment and no tax withholding. Dollar amounts are planning values. Use the official form's filing branches; a displayed line is not automatically a required entry on a filed return. The 2026 examples apply published 2026 contribution limits with the 2025 allocation structure.

January conversion followed by a $63,000 incoming rollover
Form 8606 line	Modeled amount
1	$0.00
2	$7,000.00
3	$7,000.00
4	$0.00
5	$7,000.00
6	$63,000.00
7	$0.00
8	$7,000.00
9	$70,000.00
10	0.100000
11	$700.00
12	$0.00
13	$700.00
14	$6,300.00
16	$7,000.00
17	$700.00
18	$6,300.00
15a	$0.00
15b	$0.00
15c	$0.00

Enter actual values rather than a pre-tax-only estimate

The line 6 snapshot is generally fair market value of the applicable IRA accounts, not merely their estimated pre-tax portion. Basis is accounted for in the numerator; subtracting it again from the year-end balance can double count its benefit. Market movements, residual interest and additional contributions can change the value between an estimate and December 31. Obtain the final year-end statements and reconcile them across custodians before preparing the return. A worksheet saved in October remains an estimate of a later snapshot.

The calculator's year-end fields should describe assets actually left after the modeled conversions and transfers, while conversions are entered separately. If the IRA held $28,000 before a $7,000 conversion and $21,000 remains at year end, enter $21,000 as the remaining balance. Entering $28,000 there and also entering the conversion would create a $35,000 pool under those otherwise unchanged assumptions. The December 31 simulator lets you vary the remaining value while holding the conversion fixed so this distinction is visible.

Outstanding rollovers have transaction-specific rules

Form 8606 line 6 adds certain outstanding rollovers so that a transaction spanning year end does not remove assets from the allocation merely because funds are temporarily outside an IRA. Review the exact definition in the instructions. In particular, the outstanding IRA-to-IRA rollover treatment should not be mechanically applied to an outstanding IRA-to-qualified-plan rollover. A direct transfer, a distribution eligible for rollover and a conversion are also different events. Labels such as in transit are not a complete tax analysis.

An indirect rollover can have a 60-day completion requirement, withholding concerns and other restrictions, including the one-rollover-per-year rule where applicable to IRA-to-IRA rollovers. The rule does not mean one conversion per year, and a direct trustee transfer has its own treatment. Keep the dates of distribution and receipt, source and destination account types, and custodian confirmations. If the transaction cannot be classified confidently, flag it for review rather than setting the outstanding-rollover field to zero to make a preferred result appear.

An outgoing reverse rollover requires more than a plan form

An employer plan can accept eligible pre-tax IRA dollars if its terms permit, but after-tax IRA basis generally cannot be rolled into that plan under the IRA-to-plan rule. SIMPLE restrictions, required minimum distributions and other excluded amounts can affect eligibility. An approved form, mailed check or pending custodian instruction does not by itself establish that a modeled reduction in December 31 IRA value is correct. Ask the plan administrator what must be completed, what evidence will be issued and how an outstanding transfer is reported.

For a simple projection with $7,000 basis, a $7,000 conversion and $21,000 remaining eligible pre-tax IRA assets, removing that $21,000 from the applicable year-end IRA balance changes the ordinary conversion allocation to tax free. That projection assumes a valid transaction and the correct year-end treatment. It is not a promise that a last-minute request will be processed on time. Start early enough to resolve plan acceptance, establish any eligible plan and correct paperwork without relying on a holiday-week deadline.

Use a calendar-year reconciliation process

Before converting, list known accounts and anticipated incoming or outgoing rollovers. During the year, update the model after a job change, a SEP contribution, a SIMPLE transaction or an additional conversion. Near year end, request realistic processing timelines from each custodian and receiving plan. After year end, replace projections with the actual statements and applicable outstanding-rollover treatment. Keep contribution tax years distinct from conversion calendar years throughout the process, especially for deposits made during the following spring.

Then reconcile Forms 1099-R, 5498 and 8606 with the ledger. A custodian form may be correct for that custodian while still failing to answer the aggregate-basis question. Do not alter a valid contribution year merely to align two forms issued for different calendar years. Use the deadline tool for a planning calendar and the document checklist for missing evidence. A review of the entire year's records is what supports the final return; an early conversion screenshot or an account balance observed on the transaction date cannot substitute for it.

About the publisher: Moss Ladder

Moss Ladder owns and publishes RothProRata.com, an independent educational website about IRA basis, Roth conversions and Form 8606. The guides connect official sources with invented examples, document checklists and browser-local planning tools.

AI-assisted tools help prepare explanations and software. Numerical allocation examples state their assumptions and are checked with automated calculations. These engineering checks do not constitute independent CPA or Enrolled Agent review, and no professional tax credential is claimed.

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Official sources

Source year and transaction type matter. Citations support the explanation; they do not imply government endorsement.