Retirement is the finish line millions of Americans spend decades working toward, but crossing it does not end the conversation with the IRS. Social Security benefits, the cornerstone of most retirement income plans, are subject to federal taxation for a large share of recipients.
Not anyone understands exactly how that tax is calculated over their retirement savings and what new rules now apply. This is one of the most valuable things a retiree can do before filing in 2026.
The Retirement Tax Formula the IRS Uses
The first thing every retiree needs to understand is that Social Security is never fully taxed. At most, 85% of benefits can be included in taxable income; a ceiling that applies even to the wealthiest retirement households. The floor is zero: retirees with low combined income owe nothing on their benefits at all.
The taxable amount of Social Security benefits depends on filing status and a figure the IRS calls “combined income“: adjusted gross income, plus nontaxable interest earnings, plus half of Social Security benefits. Retirement account withdrawals, pension payments, part-time wages, dividends, and capital gains all feed into that calculation.
The Two-Tier Retirement Taxing System: 50% and 85%
The thresholds that trigger taxation are fixed at $25,000 for single filers and $32,000 for married couples filing jointly — and unlike standard deductions and income tax brackets, these Social Security base amounts are not adjusted for inflation each year.
That design has quietly expanded the retirement tax burden for decades: as benefits rise with annual cost-of-living adjustments, more retirees cross the thresholds even without any real increase in purchasing power.
Retirement income that pushes combined income above the base threshold does not trigger immediate full taxation. For single filers with combined income between $25,000 and $34,000, and married couples between $32,000 and $44,000, up to 50% of Social Security benefits may be taxable. Once combined income exceeds $34,000 for singles or $44,000 for joint filers, up to 85 percent of benefits can be included in taxable income.
A worked example clarifies how this plays out in practice. A single retiree receiving $22,800 annually in Social Security who also collects $18,600 in other retirement income would have a combined income of $30,000 — above the $25,000 base. The taxable portion would be $2,500, calculated as half of the $5,000 by which combined income exceeds the threshold.
The $6,000 Senior Deduction Retirement Households Cannot Ignore
The most significant retirement tax development in years arrived when President Donald Trump signed the One Big Beautiful Bill Act into law in 2025. For tax years 2025 through 2028, taxpayers age 65 or older may claim an additional $6,000 deduction per person on top of the standard deduction already available to seniors.
For a married couple where both spouses qualify, the combined benefit reaches $12,000. The deduction is available to eligible taxpayers whether they itemize or take the standard deduction, and it phases out for those with modified adjusted gross income above $75,000 for singles and $150,000 for joint filers.
The phaseout reduces the deduction by $60 for every $1,000 of income above those thresholds, eliminating it entirely at $175,000 for single filers and $250,000 for joint filers.
For a retirement household that illustrates this concretely: an unmarried 65-year-old receiving $30,000 in Social Security and withdrawing $45,000 from a traditional IRA, with $5,000 in interest and dividends, would total $75,500 in taxable income before deductions. Applying the standard deduction of $16,100, the additional senior deduction of $2,050, and the new $6,000 temporary deduction brings taxable income down to $51,350 — a meaningful reduction in the retirement tax bill.
Why the New Deduction Carries a Long-Term Retirement Risk
The short-term relief has a structural cost that retirement advocates are raising loudly. Revenue collected from taxing Social Security flows directly back into the program’s trust fund. The expanded senior deduction reduces that revenue stream, and the Congressional Budget Office projects the Old-Age and Survivors Insurance trust fund could be exhausted within the next decade if current trajectories hold.
Trust fund depletion does not mean retirement benefits disappear — the program can continue paying benefits from ongoing payroll tax revenue — but it does mean automatic cuts to monthly checks unless Congress acts. The three-year retirement tax window may carry consequences that outlast the benefit.
State-level retirement taxation: where you live still matters
Federal rules are only part of the picture. Nine states continue to tax Social Security benefits in 2026: Colorado, Connecticut, Minnesota, Montana, New Mexico, Rhode Island, Utah, Vermont, and West Virginia. Forty-one states and the District of Columbia leave retirement benefits from Social Security entirely untouched at the state level.
West Virginia completes its phase-out in 2026, meaning benefits are fully exempt on returns filed in 2027. For retirees in states that still tax, the combined federal and state burden can be substantial enough to factor into retirement location decisions.