Guide · Social Security
How much of your Social Security is taxable?
Some of your Social Security benefit may be taxed, and some of it never is. Which part depends on a figure called provisional income — and because the thresholds don't move with inflation, more retirees cross them every year. Here's how the calculation works, and where it stops.
It runs off provisional income
The IRS decides how much of your benefit is taxed using "provisional income" — your adjusted gross income, plus any tax-exempt interest, plus half of your Social Security benefit. That last piece is the surprise: half of the benefit is folded back in to decide whether the benefit gets taxed. Provisional income isn't a number you'll see on a paystub, but it's the one that drives the whole result.
The thresholds, and the two steps up
Below the first threshold, none of your benefit is taxable. Above it, first 50% and then up to 85% of the benefit becomes taxable as your other income climbs. The thresholds are $25,000 and $34,000 for single filers, and $32,000 and $44,000 for married couples filing jointly. Crucially, these figures are not indexed for inflation — they've been fixed for decades — so as benefits and other income rise with prices, more households cross them every single year.
85% is the ceiling
There's a hard stop. No more than 85% of your benefit is ever taxed — 85% is the statutory ceiling. That matters for planning: once your other income is high enough that 85% of the benefit is already taxable, the "torpedo has fired." More income can't pull any additional benefit into tax, because there's none left to pull. Below that point, though, each extra dollar of ordinary income can drag more of your benefit in alongside it, which is why a withdrawal can cost more than its bracket suggests.
A worked example
A household receives $58,000 in Social Security for the year and has enough other income to be well past the top threshold. At the 85% ceiling, $49,300 of that benefit counts as taxable income — 85% of $58,000. The remaining $8,700 is never taxed, no matter how much more the household earns. Because they've already hit the ceiling, another IRA withdrawal won't pull any more of the benefit into tax — the torpedo has fully fired.
How Harbor handles it
Harbor computes the taxable share of your benefit from your full income picture — the same provisional-income worksheet the IRS uses — and shows how much of your Social Security lands in taxable income for the tax year you're modeling. It also flags whether you've hit the 85% ceiling, which tells you whether adding more income this year will drag more of your benefit in or not. Most states don't tax Social Security at all, and Harbor reflects your state's treatment separately. If you're weighing when to claim, the tax torpedo is worth reading about alongside the timing decision itself.
See how much of your benefit is taxed
Enter your income and Harbor shows the taxable share of your Social Security and whether you've hit the 85% ceiling.
Start planning — it's free →Common questions
Is my Social Security taxed?
It depends on your provisional income — your adjusted gross income, plus tax-exempt interest, plus half of your Social Security benefit. Below the first threshold ($25,000 single, $32,000 married filing jointly) none of your benefit is taxed. Above it, 50% and then up to 85% of the benefit becomes taxable as your other income rises. Most states don't tax Social Security at all.
What is the 85% rule?
85% is the statutory ceiling on how much of a Social Security benefit can ever be taxed — no more than 85% of your benefit is included as income, no matter how high your other income goes. Once your income is high enough that 85% is already taxed, more income can't pull any more of the benefit in, because none is left to pull. That's the point where the tax torpedo has fully fired.