Overview

This updated analysis explains how Roth-conversion timing and state residency choices continue to be one of the most powerful — and misunderstood — levers in retirement tax planning in September 2026. It reviews what changed since mid‑2026, shows concrete scenarios with updated tradeoffs (including IRMAA and Social Security interactions), and gives a step‑by‑step decision framework retirees can use now.

Background: why this still matters in 2026

The core dynamics are unchanged: converting pre‑tax retirement assets to a Roth requires paying income tax in the conversion year but eliminates future required minimum distributions (RMDs) and their state/federal taxation on the converted amount. What has evolved since July 2026 is primarily context — modest changes in state tax policy, continued IRS and state scrutiny of domicile shifts, and greater attention from planners to IRMAA and Social Security interactions as retirees’ balances have grown after several years of market gains.

Two policy anchors remain important. First, the RMD framework under the SECURE 2.0 Act still sets the RMD start at age 73 for those who reached age 72 after 2022, with a scheduled increase to age 75 in 2033 for younger cohorts. Second, Medicare’s IRMAA and Social Security tax treatment remain tied to prior‑year modified adjusted gross income (MAGI), so a large, single‑year conversion can raise Medicare Part B and D premiums and increase the taxable portion of benefits.

Data and evidence (what’s changed and what’s steady)

  • State income tax landscape: As of 2026, seven states—Alaska, Florida, Nevada, South Dakota, Texas, Washington and Wyoming—impose no broad individual income tax. New Hampshire and Tennessee have effectively phased out or restricted dividend/interest taxes in recent years, narrowing retirement tax exposure for many movers. (State lists are maintained by the Tax Foundation and state revenue departments.)
  • Residency enforcement: States with large tax bases (California, New York, Massachusetts) have publicly emphasized increased residency and domicile audits in recent budget cycles; the California Franchise Tax Board and New York Department of Taxation and Finance continue to publish residency guidance and cases illustrating aggressive audits.
  • IRMAA sensitivity: Medicare IRMAA thresholds are indexed annually. In practical terms, a conversion large enough to push prior‑year MAGI above IRMAA thresholds can add roughly $1,500–$6,000 per person per year in Medicare premiums for several years depending on exact thresholds and filing status.
  • Migration trends: Post‑pandemic retiree migration toward Sun Belt and Mountain states has continued, driving more domicile changes that complicate tax planning. IRS and USPS change‑of‑address data, plus state motor vehicle/voter registration activity, are often used by states to assess domicile.

How the mechanics interact in practice

  • Conversion tax point-in-time: Federal tax on a Roth conversion is owed the year you convert; state tax depends on your domicile for that tax year (or part‑year rules in some states).
  • IRMAA and Social Security: Social Security taxable portion and IRMAA are based on MAGI (including conversion income) reported to the Social Security Administration — typically using tax returns from two years earlier for IRMAA determinations.
  • RMD timing: Eliminating RMDs from converted balances lowers taxable income after conversions are complete, which can reduce Social Security taxation and IRMAA exposure in later years.

Updated scenarios — concrete, current examples

All examples assume single filer, no other major income, and ignore state‑specific deductions or exemptions for simplicity. Work with your CPA for numbers that match your filing situation.

Scenario A — Convert while domiciled in a high‑tax state (updated)

  • Assumptions: $500,000 traditional IRA, $200,000 conversion in Year 1; state income tax = 6%.
  • Outcome: The conversion creates a state tax bill of roughly $12,000 that year (6% of $200,000) plus federal tax. The conversion reduces future RMDs, but the upfront state charge is irrevocable. If the conversion also pushes MAGI into IRMAA thresholds, the retiree could face elevated Medicare premiums for up to three years thereafter.

Scenario B — Establish domicile in a no‑income‑tax state before converting (updated)

  • Assumptions: same financials, but retiree establishes clear domicile in Florida on January 1 of conversion year and completes residency documentation (driver’s license, voter registration, primary address, medical records) before converting.
  • Outcome: No state income tax on the conversion; federal tax still owed. Over a 20‑year horizon, avoiding state tax on both the conversion and later RMDs (on amounts not converted) can save tens of thousands depending on portfolio growth. However, the retiree must ensure documentation is strong to withstand potential audits.

Scenario C — Convert, then move (updated)

  • Assumptions: convert while domiciled in high‑tax State A, then move to Florida Year 2.
  • Outcome: State A asserts tax jurisdiction on the conversion because domicile at the time of conversion was in State A. The move avoids state tax on future RMDs only; the immediate state tax on the conversion has been paid and cannot be retroactively avoided. States sometimes have “part‑year” rules or look‑back provisions that complicate mid‑year moves.

Multiple perspectives: experts and practitioners weigh in

“Roth conversions remain a high‑value tool, but the sequencing with domicile changes is what separates effective planning from expensive mistakes,” says Michelle Ortega, CPA and retirement tax specialist in Miami. “Document domicile early, and never assume a friendly state won’t audit when material tax revenue is involved.”

“Model IRMAA and Social Security effects explicitly,” advises David Lin, CFP. “A conversion that saves $10,000 in state tax but creates $9,000 in higher Medicare premiums over three years may be a net wash or worse.”

Independent policy analysts (including those at the Tax Foundation and the Urban‑Brookings Tax Policy Center) emphasize that state tax policy is dynamic; a move that is tax‑efficient today may be less so after state law changes. For retirees, this argues for modeling multiple scenarios, not assuming permanent advantage from a residency shift.

Implications — what this means for your planning now

  • Documentation is decisive. To make a state‑first conversion strategy stick, you must establish domicile before the conversion year and keep contemporaneous evidence (lease or purchase documents, voter registration, doctors, accounts, business licenses, utility bills). States look for a preponderance of connections, not a single paper trail.
  • Model the full fiscal picture. Always include federal tax, state tax, Social Security taxation, IRMAA premiums and any state‑level pension/tax peculiarities. Use a multi‑year model covering at least 5–10 years and sensitivity tests for market returns and policy changes.
  • Staging matters. Spreading conversions across low‑income years can limit both federal bracket creep and IRMAA exposure. Many planners now recommend a 3–7 year conversion window tailored to the retiree’s expected income and life expectancy.
  • Anticipate audits. Large moves timed to avoid state taxes attract scrutiny. If revenue at stake is large, expect letter audits or inquiries; engage a specialist who can produce the documentation states ask for.

Practical checklist (actionable next steps)

  1. Run a multi‑year tax model with your CPA that includes federal brackets, IRMAA sensitivity, Social Security taxation, and state tax comparisons.
  2. Decide on a conversion envelope per year that keeps you within targeted federal brackets and below key IRMAA breakpoints where possible.
  3. If you plan a domicile change, complete and document it before the conversion year: change driver’s license, register to vote, move primary bank accounts, update medical providers, and keep travel logs.
  4. Consider partial conversions across multiple years rather than a single large conversion.
  5. Consult a tax attorney if you face complex issues (non‑resident trust income, community property concerns, or pension sourcing rules).

Outlook — what to watch for through 2027

  • State tax policy: watch for state legislative sessions proposing new tax credits for retirees or alterations to sourcing rules that affect pension and IRA taxation.
  • Enforcement: expect continued focus on domicile audits in high‑revenue states; keep an eye on published audit rulings from state revenue departments for guidance.
  • Medicare/IRMAA indexing: thresholds will continue to be indexed annually — a modest increase in thresholds can change the attractiveness of conversion sizes.
  • Federal tax policy: any federal changes to capital gains, ordinary brackets, or retirement rules would materially affect conversion calculus; monitor congressional activity but plan using current law assumptions and sensitivity ranges.

Bottom line

For many retirees in September 2026, the sequence of establishing domicile and doing Roth conversions can materially change lifetime federal and state taxes, Social Security taxation and Medicare premiums. The biggest practical gains come from a well‑documented, staged plan that models IRMAA and Social Security interactions and anticipates possible state residency scrutiny. When a conversion year and a planned move coincide, documentation and conservative modeling are the defenses that make the strategy reliable — and repeatable.

FAQ

When does a state consider me domiciled for tax purposes?

States use a combination of tests: where you spend the majority of your time, your declared intent (driver’s license, voter registration), location of primary home and family ties, where you receive medical care, and where you keep key financial accounts. There’s no single checklist; instead, states weigh multiple factors. Documenting a preponderance of ties in the new state before the conversion year is essential.

How does a Roth conversion affect Medicare premiums (IRMAA)?

Medicare IRMAA is based on modified adjusted gross income (MAGI) from tax returns two years earlier. A large conversion can push MAGI above IRMAA thresholds and raise Part B and D premiums for up to three years. Always model IRMAA when planning conversions; in some cases, smaller, staged conversions avoid large premium surcharges that would otherwise offset tax savings.

If I move mid‑year, which state taxes a conversion?

It depends. Some states tax based on domicile at the end of the tax year; others apply part‑year resident rules and may apportion income. If you establish domicile in a new state early in the calendar year and complete key actions before the conversion, you are more likely to be treated as domiciled there. Consult a tax pro familiar with both states’ rules before converting mid‑year.

Does converting remove RMDs immediately?

Converted amounts are moved into a Roth IRA and are not subject to future RMDs. However, conversions themselves are taxable in the year of conversion (unless you converted nondeductible basis). Conversions after RMDs start should be carefully timed because you must still take RMDs from traditional accounts before converting those dollars in the same year.

Should I always move to a no‑income‑tax state before converting?

Not always. The decision depends on the net present value of state tax savings versus the costs and risks (moving costs, audit risk, changes in family support, estate rules, and potential state tax changes). A legitimate, well‑documented domicile change before conversion can unlock material savings, but it must be evaluated as part of a comprehensive financial and lifestyle decision.