The best time to convert a traditional IRA to a Roth IRA is right now — specifically before December 31, 2026, when today’s historically low income tax rates are scheduled to expire and revert to higher levels under the original Tax Cuts and Jobs Act sunset provisions. If you are between age 59 and 73, have money sitting in a traditional IRA or 401(k), and expect your income or tax rate to rise in retirement, a Roth conversion this year could save you tens of thousands of dollars in lifetime taxes. The window is real, it is closing, and the math strongly favors acting before the clock runs out.

Why is 2026 such a critical year for Roth conversions?

Under current law, the tax cuts passed in 2017 were always meant to be temporary. Unless Congress acts — and as of mid-2026, the outcome remains uncertain — the top individual tax brackets snap back on January 1, 2027. The 22% bracket, for example, could jump to 25%. The 24% bracket could climb to 28%. For retirees with substantial traditional IRA balances, that difference is not trivial. A $100,000 conversion taxed at 22% costs $22,000. At 28%, that same conversion costs $28,000 — a $6,000 difference on a single transaction. Run that math across several years of conversions and the stakes become very clear.

A Roth conversion works like this: you move money from a pre-tax account (like a traditional IRA) to a Roth IRA, pay ordinary income tax on the amount converted in that tax year, and then let the money grow tax-free forever. Future withdrawals from the Roth are tax-free, and — crucially — Roth IRAs have no required minimum distributions (RMDs) during your lifetime.

What are the RMD rules for 2025 and 2026, and how do they affect conversions?

Under the SECURE 2.0 Act, the age at which you must begin taking required minimum distributions (RMDs) — mandatory annual withdrawals from traditional IRAs and most workplace retirement accounts — is now 73. If you turn 73 in 2026, your first RMD is due by April 1, 2027. Here is the critical rule: you cannot convert an RMD to a Roth. You must take your RMD first, and only then can you convert additional funds. So if RMDs apply to you, plan your conversion amounts carefully around that requirement. For people who have not yet hit RMD age, this year’s window is especially powerful — you have full flexibility over how much to convert.

For 2026, RMD amounts are calculated using the IRS Uniform Lifetime Table based on your account balance as of December 31, 2025. Work with a tax advisor or use the IRS worksheet to calculate your exact figure before planning any conversion.

How much of your Social Security income is taxable — and how does a Roth conversion affect that?

This is where the planning gets layered. Up to 85% of your Social Security benefit can be taxable, depending on your “combined income” (adjusted gross income plus non-taxable interest plus half your Social Security benefit). A large Roth conversion in a single year spikes your AGI, which can push more of your Social Security into taxable territory for that year. The strategy, then, is to convert in amounts that keep you within a comfortable tax bracket without crossing into a higher one or triggering the 85% Social Security tax threshold unnecessarily.

For 2026, the combined income thresholds that cause up to 85% of Social Security to be taxable are $34,000 for single filers and $44,000 for married couples filing jointly. Strategic, staged conversions — spreading them across multiple years — can help you stay below these thresholds while still moving significant money into your Roth.

How do Roth conversions interact with Medicare IRMAA surcharges?

IRMAA stands for Income-Related Monthly Adjustment Amount — it is the surcharge higher-income Medicare beneficiaries pay on top of the standard Part B and Part D premiums. For 2025, the standard Medicare Part B premium is $185.00 per month. But if your income from two years prior exceeds certain thresholds, you pay significantly more. For 2026 Medicare premiums, the IRS looks at your 2024 tax return. For 2027 premiums, it will look at your 2026 return — which is the year you are converting.

This means a large Roth conversion in 2026 could trigger IRMAA surcharges on your 2028 Medicare premiums. The first IRMAA tier for 2025 begins at $106,000 for individuals and $212,000 for couples. Before converting a large sum, model out what your 2026 modified adjusted gross income (MAGI) will look like and whether it crosses any IRMAA tier. In many cases, a slightly smaller conversion still delivers enormous tax savings while keeping you below an IRMAA threshold.

When should you claim Social Security to maximise your benefit?

For most people, delaying Social Security past your full retirement age (FRA) — which is 67 for anyone born in 1960 or later — increases your monthly benefit by 8% per year up to age 70. That guaranteed 8% annual growth is hard to beat. Here is how Roth conversions and Social Security timing intersect beautifully: if you retire before claiming Social Security, you may have several years of relatively low taxable income — the ideal window to convert at lower tax rates before RMDs and Social Security payments both kick in and push your income higher. Coordinating your conversion years with your Social Security claiming strategy is one of the most powerful moves in retirement tax planning.

What is the smartest way to execute a Roth conversion before year-end?

Here is a practical checklist to act on before December 31, 2026:

  1. Estimate your 2026 taxable income — include wages, pension income, investment income, and any RMDs you are required to take.
  2. Identify your conversion headroom — calculate how much you can convert before hitting the next tax bracket, an IRMAA threshold, or the 85% Social Security taxation ceiling.
  3. Take your RMD first — if you are 73 or older, you must satisfy your RMD before converting any funds.
  4. Set aside cash for taxes — pay the tax bill from non-retirement funds if possible. Using Roth conversion proceeds to pay taxes reduces the long-term benefit.
  5. Initiate the conversion with your custodian — most brokerages can process this within a few days, but do not wait until late December.
  6. Work with a CPA or financial planner — the interaction between brackets, IRMAA, Social Security taxation, and RMDs makes this worth professional guidance.

The Roth conversion window is not a gimmick or a sales pitch. It is a real, time-limited opportunity created by the scheduled expiration of current tax law. Whether you convert $20,000 or $200,000, taking action in 2026 could mean paying taxes at a rate that may not be available again in your lifetime.

Frequently Asked Questions

When should I claim Social Security to maximise my benefit?

For most people, waiting until age 70 to claim Social Security delivers the highest possible monthly benefit, because your payment grows by 8% for every year you delay past your full retirement age (67 for those born in 1960 or later). If you are in good health and have other income sources to live on in the interim, delaying is usually the mathematically superior choice. However, if you have health concerns or immediate financial needs, claiming earlier may make more sense for your situation.

How much of my Social Security benefit is taxable?

Between 0% and 85% of your Social Security benefit can be subject to federal income tax, depending on your combined income (AGI plus non-taxable interest plus half your Social Security). If your combined income exceeds $34,000 as a single filer or $44,000 as a married couple, up to 85% of your benefit is taxable. Strategic income planning — including carefully sized Roth conversions — can help keep more of your benefit tax-free.

What are the RMD rules for 2025 and 2026?

Under SECURE 2.0, required minimum distributions (RMDs) from traditional IRAs and most workplace retirement accounts must begin at age 73. Your annual RMD amount is calculated by dividing your prior December 31 account balance by an IRS life expectancy factor from the Uniform Lifetime Table. Importantly, you cannot convert an RMD into a Roth IRA — you must withdraw the RMD first before converting any additional funds.

How do I avoid Medicare IRMAA surcharges?

IRMAA surcharges are triggered when your modified adjusted gross income (MAGI) from two years prior exceeds certain thresholds — for 2025 Medicare, the first tier starts at $106,000 for individuals and $212,000 for married couples. To avoid surcharges, keep your annual income below these thresholds, or if you have had a life-changing event like retirement, file Form SSA-44 with Social Security to request a reduction based on your current income. When doing Roth conversions, model your projected MAGI carefully to avoid crossing into a higher IRMAA tier.

What is the Medicare Part B premium for 2025?

The standard Medicare Part B premium for 2025 is $185.00 per month, up from $174.70 in 2024. This is the baseline amount paid by most Medicare enrollees. Higher-income beneficiaries pay more due to IRMAA surcharges, with the highest income tier paying over $560 per month. Premiums for 2026 have not yet been officially announced but are expected to increase modestly.