Last reviewed 3 August 2026
The rules measure something they call combined income: everything else on your return, plus any tax-exempt interest, plus half of your Social Security benefits. That figure is never taxed and never appears on your return. It exists only to decide how much of your benefits gets counted.
Two details in that sentence catch people out. Tax-exempt interest is added back — municipal bonds are exempt from tax on themselves but still push benefits into the taxable column. And it is half your benefits in the yardstick, but what the yardstick decides is a share of the whole.
Below the first threshold, none of your benefits count. Between the two, part does. Above the second, more does. The figures are $25,000 and $34,000 for a single filer and $32,000 and $44,000 on a joint return.
They have never been indexed for inflation. The first was set in 1983 and the second in 1993, and both are the same today. That is not an oversight anybody has been in a hurry to fix: a threshold that stays still while everything else rises quietly reaches further every year. When the first was written it was meant to catch a small minority of recipients.
Almost everything written about this quotes those two numbers as if they were rates. They are limits. In the lower band the amount counted is the smaller of half the amount you are over the first threshold, or half your benefits. Someone barely over the threshold has almost nothing counted, not half of everything.
In the upper band it is 85% of the amount you are over the second threshold, plus an amount carried up from the lower band, and the whole thing is capped at 85% of your benefits.
Here is the part that makes required withdrawals awkward. In the upper band, one extra dollar of withdrawal raises your combined income by a dollar, which brings another 85 cents of benefits into the taxable column. Your taxable income therefore rises by $1.85, not $1.
If that dollar sits in the 22% bracket, the tax it causes is 22% of $1.85 — a little over 40 cents. The bracket has not changed. What changed is how much income each additional dollar creates. In the lower band the multiplier is 1.5 instead of 1.85, and the arithmetic works the same way.
It is not a permanent surcharge. Once 85% of your benefits are being counted, the cap binds — there is nothing left to drag in, and further dollars are taxed at your ordinary bracket again. So the steepest stretch is somewhere in the middle of the range, with ordinary rates above it.
The shape is not always a single rise, either. If your benefits are small relative to the gap between your two thresholds, the lower band can hit its own ceiling — half your benefits — before you even reach the second threshold. The rate then drops back to ordinary for a stretch and climbs again after. Two separate steep sections, with flat ground in between.
This is the opposite of how tax is normally described, and it is why a general statement like "more income means a higher rate" is not a safe guide here. Where the steep parts start and stop depends on your own benefit amount and your other income, so it is not a number anybody can quote at you — which is what the calculator is for.
Once you reach a certain age, the IRS requires you to take money out of a traditional IRA or 401(k) every year — a required withdrawal. It is not optional and it is not timed by you. Once it starts, it is ordinary income arriving every year and growing as the divisor shrinks. If it lands in the band where the multiplier applies, the tax it causes is larger than the bracket suggests — and the amount grows each year whether or not you needed the money.
The two figures interact in both directions, which is why they are worth seeing together rather than one at a time.
See how much of your own benefits would count — enter your figures and it shows the combined income, both thresholds, which tier you land in, and the arithmetic that produced the answer. The required withdrawal calculator works out the withdrawal itself, and the Roth conversion calculator shows what a conversion does to both at once. Also on this site: your retirement timeline and the joint life table.
Estimates and general information only — not tax, investment, or financial advice, and not a substitute for your own tax professional. Not affiliated with the Social Security Administration, the IRS, or any government agency. The figures here are federal only; several states tax Social Security benefits under their own rules. Tax rules change; check figures against current official materials before acting on them.