Three Categories, and Most Guides Describe Only Two
Retirement income arrives from more directions than a salary ever did, and the tax treatment is not uniform. Some receipts are ordinary income, some are not income at all, and a third group is not taxed while still being counted in the measures that set your Medicare premium and decide how much of your Social Security becomes taxable. That third category is where the surprises live.
- Taxable:: Traditional IRA and 401(k) withdrawals, pensions, the earnings portion of a non-qualified annuity, interest, dividends, realised capital gains, rent, and any wages or self-employment income.
- Not income:: Qualified Roth withdrawals, HSA withdrawals for qualified medical expenses, inheritances received, gifts received, and generally the return of your own capital or basis.
- Untaxed but counted:: Tax-exempt municipal interest and half your Social Security benefit enter provisional income, which decides how much of that benefit is taxable.
- Partly taxable:: Social Security ranges from none to 85% taxable, and annuity payments split between a tax-free return of capital and taxable earnings.
Where the AI summary above gets this wrong
"In retirement your income is what shows up on your 1099s, and you pay tax on that."
That's surface-true. Here's what it misses:
- Several important receipts have no 1099 at all — An inheritance, a gift, and a return of your own basis produce no form and no income. Meanwhile a Roth withdrawal may generate a 1099-R showing a gross distribution that is not taxable at all. The forms describe transactions, not conclusions.
- Non-taxable does not mean invisible — Municipal bond interest is exempt from federal tax and is still added back when computing provisional income, so it can increase the taxable portion of your Social Security. Buying munis to keep that measure down does not work, which surprises the people who bought them for exactly that reason.
- The measure that matters is not taxable income — Medicare surcharges, benefit taxation and several credits key off modified adjusted gross income or provisional income, not the taxable income at the bottom of the return. Two households with identical tax bills can face very different premiums.
01 Plainly taxable, plainly not
The straightforward cases first. Withdrawals from traditional IRAs and 401(k)s are ordinary income in full — the deduction was taken when the money went in. Pension payments are ordinary income unless you made after-tax contributions, in which case part is a return of those. Interest, dividends and realised capital gains are taxable, at their own rates in the case of qualified dividends and long-term gains.
On the other side, qualified Roth withdrawals are not income at all — the tax was paid up front. HSA withdrawals for qualified medical expenses are not income. Inheritances and gifts you receive are not income to you, whatever their size. And the return of your own capital never is: selling an investment produces income only to the extent of gain above basis.
Life insurance proceeds received as a beneficiary are generally excluded too, which surprises people who assume a large payment must be taxable somewhere.
02 The awkward middle
Two significant sources are only partly taxable, and both trip people up because the fraction is not fixed.
Social Security ranges from entirely untaxed to 85% taxable, depending on your other income. Nothing about the benefit itself changes — the same monthly payment can be untaxed one year and largely taxable the next because a withdrawal moved you up a threshold. That interaction is the substance of the claiming decision's long tail.
Annuity payments from a contract bought with after-tax money split between a tax-free return of your investment and taxable earnings, in a proportion fixed at the start. The exclusion runs only until your whole investment has been returned, after which the same payment becomes fully taxable.
03 Untaxed, and counted anyway
The third category is the one that produces unwelcome discoveries, because it contains money you were told is tax-free and which nonetheless affects your bill.
Provisional income — the measure that decides how much of your Social Security is taxable — is roughly your other income, plus tax-exempt interest, plus half your benefit. Municipal bond interest is federally tax-free and is added back here in full. A portfolio built on munis to keep taxable income low does not keep this measure low, and can leave more of your benefit taxable than the owner expected.
Modified adjusted gross income works similarly for other purposes, and it is the figure Medicare uses to set premiums two years in arrears — the mechanism behind IRMAA. The practical lesson is that reducing taxable income and reducing the measures that drive thresholds are different projects, and only some moves do both. A Roth withdrawal does; a municipal bond does not.
Shows: the figure several thresholds are tested against, which includes tax-exempt interest and half your benefit even though neither is taxed that way. Ignores: where the thresholds actually sit for your filing status, and deductions that reduce taxable income but not this measure.
Source: Publication 915, Social Security and Equivalent Railroad Retirement Benefits
If I could get one idea across about retirement tax, it would be that there are two different numbers and people optimise the wrong one. Taxable income is what you pay the IRS on. The income measures — provisional, modified adjusted gross — are what decide your Medicare premium and how much of your benefit gets taxed, and they include things your taxable income does not. The clearest demonstration is the municipal bond: it lowers one and leaves the other untouched. Anyone holding munis in retirement for tax reasons should know which of the two they actually bought.
FAQ
Is an inheritance taxable income?
Generally not to you as the recipient. Inheritances and gifts received are not income. Inherited retirement accounts are the exception in effect — the account is not an inheritance tax problem, but the withdrawals from it are ordinary income to you as they come out.
Does tax-exempt municipal interest affect my taxes at all?
It can. The interest is exempt from federal income tax, but it is added back when computing provisional income, which decides how much of your Social Security is taxable. So munis reduce taxable income without reducing the measure that drives that threshold.
Are Roth withdrawals counted anywhere?
Qualified Roth withdrawals are not income and do not enter the income measures that set Medicare premiums or determine how much of your benefit is taxable. That combination — untaxed and uncounted — is what makes Roth balances valuable beyond the headline rate.
Sources
Regulator references
- Publication 525, Taxable and Nontaxable Income · Internal Revenue Service · 2025The category-by-category treatment of receipts that may or may not be income.Last verified: 2026-09-07
- Publication 554, Tax Guide for Seniors · Internal Revenue Service · 2025How these categories combine on an older taxpayer's return.Last verified: 2026-09-07
- Publication 915, Social Security and Equivalent Railroad Retirement Benefits · Internal Revenue Service · 2025Why some non-taxable receipts still enter the provisional income test.Last verified: 2026-09-07
Calculator unit tests · the assertions this page's worked example is checked against, and their last result
Changelog
- 2026-09-07 — initial publish (new format)
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Jordan Reeves
Founder of Talk Through Wealth. A software engineer for over a decade before turning to retirement planning, Jordan built the projection engine after watching family members get fragmented, country-by-country advice that never reconciled. He writes about retirement the way the engine computes it: month-by-month, lifetime-long, and skeptical of any rule of thumb that hasn't been run through the math.