How to Actually Calculate Your Retirement Tax Burden

Step One: Add Up All Your Income Sources

The first step in calculating your retirement tax bill is listing every income source. Unlike your working years where income was mostly one line on your pay stub, retirement income arrives from multiple directions - and each source has different tax treatment. For this example, we will use a married couple at age 74 with the following income. Social Security: $40,000 per year ($20,000 each). Pension income: $30,000 per year from a former employer defined benefit plan. Required Minimum Distributions: $25,000 per year from a combined $680,000 in traditional IRAs. Investment income from a taxable brokerage account: $10,000 per year in dividends and interest. Before calculating taxes, you need to know which income counts as ordinary income (taxed at bracket rates), which qualifies as long-term capital gains (potentially taxed at 0%, 15%, or 20%), and which is partially or fully excluded from taxation altogether. In our example: the $30,000 pension is fully ordinary income. The $25,000 RMD is fully ordinary income. The $10,000 investment income - if it consists primarily of qualified dividends and long-term gains - may be taxed at preferential rates. The Social Security is handled through its own formula, which we will calculate in the next step. Total gross income before any tax calculations: $105,000. But your taxable income will be substantially different once we run each component through its proper formula. Note the 2026 standard deduction for married couples filing jointly: $32,200. For couples where both spouses are 65 or older, there is an additional deduction of $1,600 per person, bringing the total to $35,400. This reduces taxable income before you even apply the brackets.

Step Two: Calculate How Much Social Security Is Taxable

Social Security taxation is calculated separately from the rest of your income using the combined income formula. Combined income equals your adjusted gross income, plus any tax-exempt interest you earned, plus half of your Social Security benefit. For our example couple: their AGI before Social Security taxation = $30,000 pension + $25,000 RMD + $10,000 investment income = $65,000. Half of Social Security = $20,000. Combined income = $65,000 + $20,000 = $85,000. Now compare that combined income to the IRS thresholds for married filing jointly filers. Below $32,000: zero Social Security is taxable. Between $32,000 and $44,000: up to 50% of Social Security is taxable. Above $44,000: up to 85% of Social Security is taxable. At $85,000 combined income, our couple is well above the $44,000 threshold. This means up to 85% of their $40,000 Social Security benefit is taxable. 85% of $40,000 = $34,000 added to their taxable income. Here is the calculation that surprises most people: the couple's gross income is $105,000, but their adjusted gross income for tax bracket purposes now becomes $65,000 + $34,000 in taxable Social Security = $99,000. The RMDs pushed more of their Social Security into taxable territory. This interaction - where traditional IRA and 401(k) withdrawals cause Social Security benefits to become taxable - is the core mechanism behind the retirement tax trap. Every dollar of RMD income causes 85 cents of additional Social Security income to become taxable for retirees above the $44,000 married threshold.

Step Three: Apply Deductions and Calculate Federal Tax

With AGI established at $99,000, the next step is applying deductions to arrive at taxable income. For our couple, both age 74 and married filing jointly: standard deduction is $32,200, plus two additional $1,600 deductions for being over 65 = $35,400 total. Taxable income: $99,000 minus $35,400 = $63,600. Now apply the 2026 married filing jointly tax brackets to $63,600 of taxable income: First $24,800 at 10% = $2,480. Next $38,800 (from $24,801 to $63,600) at 12% = $4,656. Total federal income tax: approximately $7,136. Effective federal rate on taxable income: 11.2%. Effective federal rate on gross income of $105,000: 6.8%. That sounds reasonable. But we are not done. The $10,000 in qualified dividends and long-term capital gains from the brokerage account - already included in the AGI above - needs its own rate check. If taxable income is under $94,050 for married filers in 2026, the long-term capital gains rate is 0%. Our couple at $63,600 of taxable income falls within that zone, so those gains may be taxed at 0% at the federal level. This is an important planning opportunity - keeping taxable income below the 0% capital gains threshold saves real money. For state taxes: 41 states and Washington D.C. do not tax Social Security benefits. Nine states have no income tax at all. But in a state like Minnesota or Vermont that taxes both ordinary income and Social Security, add another 5-9% state rate on applicable income. Our example couple in a 5% state income tax state would owe approximately $3,000-$4,500 more in state taxes.

Step Four: Check Your IRMAA Exposure

Federal income tax is not the final bill. If your MAGI - adjusted gross income plus tax-exempt interest - exceeded certain thresholds two years ago, you owe Medicare IRMAA surcharges on top of your standard Part B premium. IRMAA uses a two-year lookback. In 2026, the surcharges are based on your 2024 income. For single filers with 2024 MAGI of $109,000 or less, the standard Part B premium is $202.90 per month with no surcharge. For married couples, the threshold before surcharges begin is approximately $218,000. For our example couple, 2024 MAGI was approximately $99,000. They fall well below the married threshold, so no IRMAA surcharge applies. But consider a slightly different scenario: the same couple has a $50,000 Roth conversion in 2024 on top of their regular income, bringing 2024 MAGI to $149,000. That is still below the $218,000 married threshold - they remain in the clear. Now suppose one spouse has a pension of $60,000 instead of $30,000, and RMDs of $40,000. Their 2024 MAGI could easily reach $170,000. If combined income crosses $218,000, they enter the second IRMAA tier and each spouse pays an additional $81.20 per month in Part B surcharges - $162.40 per month combined, or $1,949 per year in extra Medicare premiums. A $324.60/month per-person surcharge kicks in at the next tier. The IRMAA cliff effect is severe: even one dollar over a tier threshold triggers the full surcharge for that tier. This makes income management in the two years before Medicare enrollment, and every year after, a genuine tax optimization target.

The Full Picture: What Our Sample Couple Actually Pays

Let us add up the complete tax picture for our example couple with $105,000 in gross retirement income. Federal income tax on $63,600 of taxable income: approximately $7,136. Federal tax on qualified dividends at 0% (within the 0% LTCG bracket): $0. State income tax (assuming a 5% state on applicable income of approximately $85,000): approximately $4,250. Medicare Part B and D premiums at standard rates for two people: approximately $4,870 per year. Total annual tax and premium burden: approximately $16,256. As a percentage of gross income: $16,256 divided by $105,000 = approximately 15.5% effective total rate. That is higher than many people expect on what feels like a modest retirement income - but lower than the feared 40% effective rate. Where rates get genuinely high is at the margin. If this couple earns one more dollar of traditional IRA income, that dollar is taxed at 12% federal, it pulls 85 cents of Social Security into the 12% bracket (so 12% x 1.85 = effective 22.2% marginal rate), and in a state that taxes income it adds another 5%. The effective marginal rate on additional IRA income within the Social Security phase-in zone is not 12% - it is closer to 27-28% for this couple. For retirees with income above $100,000, the marginal rates climb further still. Use the retirement tax calculator to run your own numbers before assuming your tax situation is simpler than it is.