How will the SECURE 2.0 RMD changes for 2026 affect taxable income calculations for Social Security benefits?
Executive summary
The SECURE 2.0 changes that take effect around 2026 alter when and how much retirees must withdraw from tax-deferred accounts and change several Roth and employer-plan rules; those changes can materially affect the Modified Adjusted Gross Income (MAGI) used to determine how much of Social Security is taxable and whether Medicare IRMAA surcharges apply [1] [2] [3]. In practice the net effect depends on three levers—later RMD start ages and timing, greater use of Roth (after‑tax) treatment for catch‑ups and conversions, and tax‑sparing tools such as qualified charitable distributions (QCDs)—and those levers can either raise or lower the MAGI formula that determines Social Security taxation [4] [2] [3].
1. How SECURE 2.0 shifts RMD timing and why timing matters to Social Security taxation
SECURE 2.0 raised the RMD starting age (already moved to 73 in 2023 and scheduled to later move toward 75 for future cohorts), which delays when taxable withdrawals must be reported as income and therefore can reduce MAGI in early retirement years when Social Security benefits first become payable; delaying withdrawals can keep combined income lower and thus reduce the percentage of Social Security benefits that are included in taxable income [4] [1] [5]. The IRS finalized many implementation rules but left some administrative steps and plan amendments to 2026 deadlines, creating a patchwork of effective dates that makes exact calculations situation‑specific [6] [7].
2. The MAGI/computed “combined income” formula that determines how much Social Security is taxed
Taxability of Social Security benefits is computed from combined income—generally MAGI plus half of Social Security—which means taxable RMDs raise that base directly and can push a retiree from 0% to 50% or 85% of benefits being taxable under federal rules; that thresholding is the direct channel by which larger RMDs increase Social Security taxable amounts and related Medicare surcharges [3]. Multiple reporting sources emphasize that when RMDs increase taxable income, they may move taxpayers into higher tax brackets and into IRMAA ranges, magnifying out‑of‑pocket costs beyond income tax alone [8] [9].
3. Roth and catch‑up rules: how “after‑tax” contributions change the future RMD/MAGI picture
SECURE 2.0’s 2026 and near‑term provisions force higher‑earning catch‑up contributions to be made as Roth (after‑tax) for many plan participants, meaning those dollars are taxed when contributed rather than when distributed and can reduce future taxable RMDs if the funds remain Roth or are rolled to Roth—thereby lowering MAGI that feeds Social Security taxation [1] [10] [2]. In addition, employer‑plan Roth changes and phased exclusions (and the IRS guidance that Roth balances in some plans will be excluded from RMD calculations in coming years) create pathways to shift future distributions out of taxable income—though the precise effective dates and plan‑level availability vary [2] [6].
4. Other available tools that can blunt RMD‑driven increases in Social Security taxability
Qualified charitable distributions (QCDs) remain a key tool because they count toward RMD obligations without being included in taxable income, thus lowering MAGI and the combined‑income formula used to tax Social Security benefits; advisers and planning guides explicitly recommend QCDs and Roth conversions timed to minimize MAGI for key years that determine Medicare IRMAA [4] [11]. Conversely, failures to take required RMDs carry stiff excise taxes (reduced under recent rules but still significant), which can create urgency to withdraw taxable sums even when those withdrawals would raise Social Security tax exposure [5].
5. The bottom line and the caveats investors must track
For many retirees the headline effect of SECURE 2.0 in 2026 is greater flexibility: later RMDs and expanded Roth pathways create realistic strategies to lower MAGI in years when Social Security taxes and IRMAA are calculated, but outcomes hinge on personal timing (when benefits start, when RMDs would have occurred) and plan‑level implementation details; IRS final regulations and notices tighten the rules but some transitional and plan‑amendment deadlines through 2026 mean practical effects will be uneven and require individualized modeling [6] [7] [4]. Advocates warn that without active planning forced taxable withdrawals can still spike MAGI and trigger higher Social Security taxation and Medicare surcharges, while proponents counter that Roth and QCD options now make it easier to control tax timing—both views are supported in the reporting [8] [9] [4].