What Is Provisional Income?
Most people have never heard the term, which is unfortunate, because it quietly decides a large part of their retirement tax bill. It has one other name you may see — "combined income" — and they mean the same thing.
The formula, in plain terms
Adjusted gross income — wages, IRA and 401(k) withdrawals, pension, dividends, capital gains, rental income, Roth conversions
+ tax-exempt interest — yes, including municipal bonds
+ one half of your Social Security benefit
= provisional income
Two things in that list surprise almost everyone.
Municipal bond interest counts. Muni interest is federally tax-free on its own, and people buy it specifically for that. But it is explicitly added back when calculating provisional income. So a tax-free bond can still increase the tax you owe on your Social Security.
Roth withdrawals do not count. Qualified withdrawals from a Roth IRA stay out of the formula entirely. That is the single most useful lever most retirees have, and it is why which account you draw from matters as much as how much you draw.
The thresholds
| Filing status | None taxable | Up to 50% taxable | Up to 85% taxable |
|---|---|---|---|
| Single | Under $25,000 | $25,000 – $34,000 | Over $34,000 |
| Married filing jointly | Under $32,000 | $32,000 – $44,000 | Over $44,000 |
These were written into law in 1983 and have never been indexed to inflation. When they were set, they affected roughly one retiree in ten. Today they reach a large share of ordinary middle-income retirees — not because anyone raised a tax, but because the line stopped moving while everything else kept going.
A worked example
A married couple, both retired. $40,000 of Social Security between them. $30,000 from an IRA. $5,000 of municipal bond interest.
| Component | Amount |
|---|---|
| IRA withdrawal (in AGI) | $30,000 |
| Municipal bond interest (added back) | $5,000 |
| Half of Social Security ($40,000 ÷ 2) | $20,000 |
| Provisional income | $55,000 |
$55,000 is above the $44,000 married threshold, so they land in the top tier and up to 85% of their $40,000 benefit — as much as $34,000 — gets added to taxable income.
Now change one thing. Suppose $15,000 of that IRA withdrawal had come from a Roth instead. Provisional income drops to $40,000, which lands in the middle tier rather than the top one. Same spending money in their pocket, materially different tax result — decided entirely by which account the money came out of.
The tax torpedo
There is a stretch of income where each additional dollar you withdraw does two things at once: it is taxed itself, and it drags more of your Social Security into taxable income. The result is an effective marginal rate meaningfully higher than your stated bracket — someone nominally in the 12% bracket can face an effective rate closer to 22% on those dollars.
This is known as the tax torpedo, and it is the reason two retirees with identical incomes can owe noticeably different amounts. It is not about how much you have. It is about the order and timing of where it comes from.
What to do with this
- Know your number before December. Provisional income is only controllable while the year is still open. Once it closes, it is arithmetic.
- Consider Roth conversions in low-income years — particularly the gap between retiring and starting Social Security, when income is often at its lowest.
- Watch one-time events. A home sale or large withdrawal can push you over a line for a single year, and it also affects your Medicare premium two years later.
- Remember muni interest counts when you are choosing where to hold bonds.
Check your own number
Three inputs, instant answer, nothing gated. The email step afterwards is optional.
| Provisional income | $0 |
| Which tier you land in | — |
| Share of benefit taxed | 0% |
We will email you a written copy showing how the math worked, what would change your tier, and the thresholds for next year. Free, and you can keep it or forward it to whoever does your taxes.
Educational follow-up by email. We never sell your information.
Common questions
What is provisional income?
Provisional income is your adjusted gross income, plus any tax-exempt interest such as municipal bond interest, plus half of your Social Security benefit. The IRS uses it to determine how much of your Social Security is taxable. It does not appear as a line on your tax return, so you have to calculate it yourself.
Do Roth withdrawals count toward provisional income?
No. Qualified withdrawals from a Roth IRA are excluded from provisional income entirely. That makes Roth accounts one of the most effective tools for keeping Social Security taxation down. Note that a Roth conversion does count in the year you convert, even though later withdrawals do not.
Does municipal bond interest count toward provisional income?
Yes. Tax-exempt interest is specifically added back when calculating provisional income, even though it is not federally taxable by itself. Municipal bonds can therefore increase the tax you owe on your Social Security benefit.
What is the tax torpedo?
The tax torpedo is the stretch of income where each extra dollar withdrawn is taxed itself and also causes more of your Social Security to become taxable. This produces an effective marginal rate higher than your stated bracket, sometimes close to double it.
Is provisional income the same as MAGI?
No, though they are often confused. Provisional income decides how much of your Social Security is taxable. MAGI (modified adjusted gross income) is used for other purposes, including IRMAA Medicare surcharges. They are calculated differently and used for different things.
These numbers change every year
The IRMAA brackets, the standard deduction and the senior deduction are all adjusted annually, and the 2027 figures are published late in 2026. The Social Security taxation thresholds are the one exception — those have not moved since 1983 and are not expected to.
We send one short email when the new numbers are announced. No campaign, no sequence — one email when there is something worth knowing.
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Run the free calculatorRelated guides
Is Social Security Taxable?The three-step check using your own numbers.What Tax Rate Do You Pay on Social Security?85% taxable is not an 85% tax.How to Reduce Taxes on Your Social SecurityFive levers that lower provisional income.The Retirement Literacy Foundation is a 501(c)(3) non-profit. This guide is general financial education, not individualized investment, tax, or insurance advice. Tax rules change and depend on your personal situation. Consider speaking with a licensed professional before making decisions.