How to Report Form SSA-1099-SM-UD on Your Tax Return

To report Form SSA-1099-SM-UD on your tax return, put the Box 5 net benefits figure on line 6a of Form 1040 or 1040-SR, then work the worksheet in IRS Publication 915 to find the taxable portion and enter that amount on line 6b.¹ Any federal tax the SSA already withheld appears in Box 6 and gets credited against your bill the same way W-2 withholding does. Everything else on the form feeds one of those two entries.

Read the Boxes Before You Report

Box 3 is your gross benefits for the year, before any deductions. That includes months when Medicare premiums or other withholdings ate up your entire deposit — those amounts still count as benefits paid to you for tax purposes.²

Box 4 is what you paid back to the SSA during the year, usually to recover an overpayment or from a returned check. Box 3 minus Box 4 gives you Box 5, and Box 5 is the number that goes on your return.²

Box 6 shows any voluntary federal income tax you asked the SSA to withhold. Most beneficiaries don’t elect withholding, so this is often zero. If there’s a number there, it flows to the withholding line of your 1040.

Where the Numbers Go on Form 1040

Line 6a: the Box 5 amount, exactly as printed. Line 6b: the taxable portion, which you calculate using the worksheet in Publication 915.³ Form 1040 and Form 1040-SR use the same line numbers here. If Social Security was your only income for the year, line 6b will almost always be zero. Once you add pension income, IRA distributions, wages, investment income, or a meaningful amount of tax-exempt interest, the worksheet starts producing a taxable figure.

How Much of Your Benefit Is Taxable

The IRS runs a calculation called provisional income (also called combined income): your adjusted gross income from non-Social-Security sources, plus any tax-exempt interest, plus half of the Box 5 amount. The result gets measured against fixed dollar thresholds.⁴

Provisional income at or below $25,000 (single) or $32,000 (married filing jointly): none of your benefits are taxable.
Between those numbers and $34,000 (single) or $44,000 (joint): up to 50 percent of your benefits are taxable.
Above $34,000 (single) or $44,000 (joint): up to 85 percent is taxable, and 85 percent is the ceiling.⁴

These thresholds have not been adjusted for inflation since Congress set them in 1983 and 1993, so cost-of-living increases push more beneficiaries across the lines each year.

If You’re Married Filing Separately

Married filing separately and lived with your spouse at any point during the year? Your base amounts are both zero. Up to 85 percent of your benefits are taxable regardless of income, and the Publication 915 worksheet skips the usual steps and multiplies Box 5 by 0.85.³ The one exception is spouses who lived apart the entire year, who use the $25,000 single-filer threshold.

Withholding Already Taken, and Setting It Up Going Forward

Whatever appears in Box 6 gets entered on your 1040 as federal income tax withheld, on the same line where you’d report W-2 withholding. It reduces your balance due or increases your refund.

If the worksheet shows you’re going to owe on your benefits and you’d rather have tax withheld than pay quarterly estimates, file Form W-4V with your local Social Security office. The SSA will only withhold at 7, 10, 12, or 22 percent of each payment — no other percentages and no dollar amounts.⁵

Lump-Sum Payments for a Prior Year

If your Box 3 amount includes a retroactive payment covering months from an earlier year, the default rule taxes the whole lump sum in the year it was paid. That can spike your provisional income and push more of your current benefits into the taxable zone than would have applied if the money had arrived on time.

The lump-sum election lets you recalculate: figure what the taxable portion would have been in the earlier year if the lump sum had been included then, subtract what you actually reported taxable for that year, and add the remainder to the current year’s taxable benefits. If that produces a smaller taxable amount than the default calculation, you use it.³ You make the election by checking the box on Form 1040 line 6c and keeping the completed worksheets 2 through 4 from Publication 915 with your records. You don’t amend the earlier return, and you can’t revoke the election without IRS consent.

If Box 4 Shows a Repayment Over $3,000

A Box 4 repayment reduces Box 5, which already handles the tax effect for most people. But if the repayment is more than $3,000, and the original benefits were taxed in a prior year, the claim-of-right doctrine gives you a choice: take a deduction in the current year for the repaid amount, or figure what your tax would have been in the earlier year without the overpaid benefits and claim a credit for the difference.⁶ You use whichever method produces the lower tax. For repayments of $3,000 or less, only the deduction is available. The calculation is one of the more error-prone spots on a return that involves benefits, and worth running past a tax preparer if the numbers are meaningful.

Medicare Premiums Deducted From Your Benefit

Part B and Part D premiums pulled from your monthly deposit are medical expenses. If you itemize on Schedule A, add them to your other qualifying medical costs; only the total above 7.5 percent of your AGI is deductible.⁷ Given the 2026 standard deduction of $16,100 for single filers and $32,200 for joint filers, plus additional amounts for taxpayers 65 and older, itemizing pays off only when your total itemized deductions clear that bar.⁸

If you have self-employment income, there’s a better route. The self-employed health insurance deduction lets you deduct Medicare premiums (including IRMAA surcharges) on Schedule 1, line 17, using Form 7206. It reduces AGI directly, with no 7.5 percent floor to clear.⁹

State Taxes Are Separate

Most states either have no income tax or fully exempt Social Security benefits. Only nine states tax any portion of Social Security income, most of them with partial exemptions tied to income, and some are phasing their taxation out. Check your state’s current-year instructions before assuming the state return follows the federal treatment.

If the Form Is Wrong or Missing

Compare Box 3 against your bank deposits and your expected monthly benefit before doing anything else. If the figures don’t match, only the SSA can issue a corrected form. Call 1-800-772-1213 (TTY 1-800-325-0778), Monday through Friday, 8:00 a.m. to 7:00 p.m., or visit your local office.¹⁰

For a missing or replacement copy, log in to your my Social Security account at ssa.gov/myaccount. The current tax year’s form is available online starting February 1, along with statements for the past six years.¹⁰

If a corrected form hasn’t arrived by your filing deadline, you can file using figures you’ve verified from your own records. Keep bank statements, correspondence with the SSA, and notes on what you reported. The IRS matches your return against the version the SSA sent them, and a documented paper trail is what resolves the notice if a mismatch triggers one.

1
Internal Revenue Service. Instructions for Forms 1040 and 1040-SR
2
Social Security Administration. POMS GN 05002.010 – Social Security Benefit Statement Box 3, Benefits Paid
3
Internal Revenue Service. Publication 915 – Social Security and Equivalent Railroad Retirement Benefits
4
Office of the Law Revision Counsel. 26 USC 86 – Social Security and Tier 1 Railroad Retirement Benefits
5
Internal Revenue Service. Form W-4V – Voluntary Withholding Request
6
Office of the Law Revision Counsel. 26 USC 1341 – Computation of Tax Where Taxpayer Restores Substantial Amount Held Under Claim of Right
7
Internal Revenue Service. Publication 502 – Medical and Dental Expenses
8
Internal Revenue Service. IRS Releases Tax Inflation Adjustments for Tax Year 2026
9
Internal Revenue Service. Instructions for Form 7206
10
Social Security Administration. How Can I Get a Replacement Form SSA-1099/1042S, Social Security Benefit Statement?