What this diagnostic can—and cannot—tell you
A “backdoor Roth” is an informal name for two separate transactions: a regular contribution to a Traditional IRA, usually reported as nondeductible, and a later conversion to a Roth IRA. The IRS does not publish a special backdoor account or form. That is why a single yes/no question is not enough.
This tool checks whether the new contribution gate appears open, whether the direct route may be available, whether the owner’s IRA pool creates a pro-rata issue, and whether the records needed to support the result are present. It does not estimate federal or state tax, IRMAA, ACA effects, investment outcomes, or whether the strategy is a good choice.
Which accounts count in the pro-rata pool?
Count for this owner
- Traditional IRA
- Rollover IRA
- Traditional SEP IRA
- Traditional SIMPLE IRA—including during its two-year restriction
Outside this owner’s pool
- Roth IRA, Roth SEP and Roth SIMPLE
- 401(k), 403(b), governmental 457(b) and TSP
- A spouse’s IRA accounts
- A properly separate nonspouse inherited IRA
Ownership matters more than the number of accounts. The IRS generally treats all of one taxpayer’s Traditional, SEP and SIMPLE IRAs as one pool under IRC §408(d)(2). Each spouse has a separate pool and a separate Form 8606, even on a joint return.
Why December 31 can change an earlier conversion
Form 8606 does not simply photograph the IRA on the conversion date. Its denominator generally combines the owner’s December 31 Traditional/SEP/SIMPLE value with relevant same-year distributions and net conversions. A March conversion can therefore be affected by a November 401(k)-to-IRA rollover. The reverse can also matter: eligible pretax IRA money accepted by a workplace plan before year-end may leave a smaller IRA pool.
That cleanup route is conditional. A receiving plan is not required to accept incoming IRA money, and only the otherwise taxable amount can move to the plan. The exact source, SIMPLE anniversary, RMDs and basis records matter. IRS Notice 2026-49 introduced proposed optional rollover-certification procedures in 2026; it did not require plans to accept rollovers or create a new substantive safe harbor.
A split-year example beginners rarely see
Suppose Maya contributes $7,500 in February 2027 and tells the custodian it is her 2026 Traditional IRA contribution. She converts the account in February 2027. The contribution belongs to 2026, but the conversion cannot be backdated: it belongs to calendar year 2027.
- 2026 Form 8606: reports the nondeductible 2026 contribution and carries the basis forward.
- 2027 Form 8606: begins with that carried basis and reports the 2027 conversion.
- December 31, 2027: supplies the conversion-year IRA-pool snapshot.
This is why “I made my 2026 backdoor in 2027” is ambiguous. The contribution can be for 2026. The conversion cannot.
Form 8606 is a basis ledger, not a one-year receipt
| Event or record | What it establishes | Where it matters |
|---|---|---|
| Nondeductible Traditional IRA contribution | New after-tax basis for the owner | Form 8606 Part I for the contribution year |
| Latest prior Form 8606 with line 14 basis | Basis carried from the last active filing year | Part I line 2; it need not be last year’s form |
| Traditional IRA-to-Roth conversion | Amount moved and potentially taxable | Parts I and II when basis is involved |
| December 31 account statements | Owner-wide Traditional/SEP/SIMPLE value | Part I line 6 and supporting workpapers |
| Form 5498 / contribution confirmation | Amount and contribution-year designation | Supporting record; Form 5498 may arrive after filing day |
| Form 1099-R / conversion confirmation | Calendar-year distribution or conversion | Return matching and Form 8606 reporting |
A year with nothing but carried basis does not automatically require a new Form 8606. Conversely, a missing recent form does not prove basis is zero. The current final instructions list possible $50 failure-to-file and $100 basis-overstatement penalties absent reasonable cause, so uncertain records deserve reconstruction rather than a guessed number.
2026 figures used by the diagnostic
| Rule | 2026 amount | Important boundary |
|---|---|---|
| Combined regular Traditional + Roth IRA limit | $7,500 under 50; $8,600 age 50+ | Eligible compensation can impose a lower limit |
| Direct Roth phaseout, Single/HoH | $153,000–$168,000 Roth MAGI | MFS living apart all year uses this range |
| Direct Roth phaseout, MFJ/QSS | $242,000–$252,000 Roth MAGI | Spousal compensation requires a joint return |
| Direct Roth phaseout, MFS living together | $0–$10,000 Roth MAGI | Living together at any time triggers this range |
These amounts are verified against IRS Notice 2025-67. High MAGI can block a direct Roth contribution, but it does not itself block a Traditional IRA contribution or Roth conversion. Deductibility is another separate test.
Conditions that should leave this simplified tool
Manual review is appropriate when the facts include an RMD, inherited IRA, withholding, a pending rollover, multiple distributions or conversions, a direct-Roth correction, missing historical basis, an employer-replaced SIMPLE plan, or an amount still in transit at year-end. Those are not necessarily errors; they simply require more facts than a deterministic triage can safely infer.
Methodology and primary sources
The rule engine is deterministic and runs locally. Unresolved inputs that control the contribution, calendar, IRA-pool or basis result cannot produce a clean status. It deliberately routes exact direct-contribution math to Can I Contribute? and exact pro-rata dollars to the Backdoor Roth Calculator.
- IRS Notice 2025-67 — 2026 IRA limits and Roth MAGI phaseouts
- IRS Publication 590-A — compensation, contributions, conversions and rollovers
- IRS Form 8606 and instructions — basis, aggregation and reporting
- IRS SIMPLE IRA withdrawal and transfer rules — two-year restriction
- IRS Notice 2024-02 — narrow terminated-SIMPLE replacement rule
- IRS Notice 2026-49 — proposed optional rollover procedures
- 2026 Instructions for Forms 1099-R and 5498 — transaction records
Currentness note: as of August 24, 2026, the 2026 Form 8606 is early-release draft only; the latest final detailed Form 8606 instructions are for 2025. The draft retains the same core lines used here. Recheck the final 2026 form before filing.