Social Security Benefits Taxability Calculator
By Forrest Baumhover, CFP®, EA · Last verified September 20, 2026
Find out how much of your Social Security or Tier 1 Railroad Retirement benefits are taxable. Every step of IRS Publication 915 Worksheet 1 shows, with its IRC §86 citation.
The dollar thresholds are fixed by statute and do not change from year to year. Line references follow Pub. 915 (2025). Last verified 2026-09-20.
How Social Security benefits become taxable
Social Security benefits are not automatically taxable, and they are never taxable in full. IRC §86 taxes at most 85% of them, and only when your other income is high enough. The calculation runs in four steps, and this calculator shows each one.
- Find provisional income. Add your other income, your tax-exempt interest, and half of your benefits, then subtract the adjustments to income Pub. 915 lists (IRC §86(b)).
- Compare it to the base amount. The base amount is $25,000 for single, head of household, and qualifying surviving spouse filers, $32,000 for married filing jointly, and $25,000 for married filing separately if you lived apart from your spouse all year. It is $0 if you filed separately and lived with your spouse at any time (IRC §86(c)(1)). At or below the base amount, none of your benefits are taxable.
- Apply the 50% tier. Between the base amount and the adjusted base amount ($34,000 single, $44,000 joint), you include the lesser of half your benefits or half the excess over the base amount (IRC §86(a)(1)).
- Apply the 85% tier. Above the adjusted base amount, you include 85% of the excess over it, plus the smaller of the 50%-tier amount or half the gap between the two thresholds, capped at 85% of your benefits (IRC §86(a)(2)).
The base and adjusted base amounts are fixed dollar figures in the statute. Unlike most tax thresholds, they do not rise with inflation, so more retirees cross them each year as their income grows.
Worked example
A single filer receives $24,000 in Social Security benefits, has $30,000 of other income, and earns $1,000 of tax-exempt interest. Provisional income is $43,000, which lands in the 85% tier. The taxable amount is $12,150, or 50.63% of benefits.
| Step | What it is | Amount | Source |
|---|---|---|---|
| Line 1 | Net benefitsBox 5 of all Forms SSA-1099 and RRB-1099Also goes on Form 1040, line 6a. | $24,000 | Pub. 915 (2025), Worksheet 1; IRC §86(a)(1) |
| Line 2 | Half of benefitsLine 1 × 50%The "one-half of the social security benefits" term of provisional income. | $12,000 | IRC §86(b)(1)–(2) |
| Line 3 | Other incomeForm 1040 lines 1z, 2b, 3b, 4b, 5b, 7a, and 8 (Schedule B line 2 in place of line 2b if you file Form 8815)Taxable income other than Social Security. | $30,000 | Pub. 915 (2025), Worksheet 1; IRC §86(b)(1)–(2) |
| Line 4 | Tax-exempt interestForm 1040, line 2aSection 86(b)(2)(B) adds it to modified AGI. | $1,000 | IRC §86(b)(1)–(2) |
| Line 5 | ExclusionsAdoption benefits, foreign earned income/housing, American Samoa/Puerto Rico incomeSection 86(b)(2)(A) computes AGI without regard to §§137, 911, 931 and 933, so you add these amounts back. | $0 | IRC §86(b)(1)–(2) |
| Line 6 | Income before adjustmentsLine 2 + line 3 + line 4 + line 5 | $43,000 | Pub. 915 (2025), Worksheet 1 |
| Line 7 | Adjustments to incomeSchedule 1 lines 11–20, 23, and 25These adjustments reduce provisional income. | $0 | Pub. 915 (2025), Worksheet 1 |
| Line 8 | Provisional incomeLine 6 − line 7Modified AGI + tax-exempt interest + half of benefits. | $43,000 | Pub. 915 (2025), Worksheet 1; IRC §86(b)(1)–(2) |
| Line 9 | Base amountSet by filing statusSingle. | $25,000 | IRC §86(c)(1) |
| Line 10 | Excess over base amountLine 8 − line 9 | $18,000 | Pub. 915 (2025), Worksheet 1; IRC §86(a)(1)(B) |
| Line 11 | Width of the 50% tierAdjusted base amount − base amount$34,000 − $25,000. | $9,000 | IRC §86(c)(2) |
| Line 12 | Excess over adjusted base amountLine 10 − line 11 (not below zero)Zero means provisional income stays inside the 50% tier. | $9,000 | Pub. 915 (2025), Worksheet 1; IRC §86(a)(2)(A)(i) |
| Line 13 | Amount inside the 50% tierSmaller of line 10 or line 11 | $9,000 | Pub. 915 (2025), Worksheet 1 |
| Line 14 | 50% of that amountLine 13 × 50% | $4,500 | IRC §86(a)(1)(B); IRC §86(a)(2)(A)(ii) |
| Line 15 | 50%-tier inclusionSmaller of line 2 or line 14Never more than half of the benefits. | $4,500 | IRC §86(a)(1); IRC §86(a)(2)(A)(ii) |
| Line 16 | 85%-tier inclusionLine 12 × 85% | $7,650 | IRC §86(a)(2)(A)(i) |
| Line 17 | Uncapped taxable amountLine 15 + line 16 | $12,150 | Pub. 915 (2025), Worksheet 1; IRC §86(a)(2)(A) |
| Line 18 | Cap: 85% of benefitsLine 1 × 85% | $20,400 | IRC §86(a)(2)(B) |
| Line 19 | Taxable benefitsSmaller of line 17 or line 18Enter on Form 1040 line 6b. | $12,150 | Pub. 915 (2025), Worksheet 1; IRC §86(a)(2) |
Illustrative inputs. Sources: IRC §86; IRS Publication 915 (2025), Worksheet 1. Last verified 2026-09-20.
How to calculate taxable Social Security benefits, line by line
This calculator follows IRS Publication 915 Worksheet 1. Lines 1 to 8 build provisional income (IRC §86(b)(1)). Take half of your benefits and add your other income, your tax-exempt interest, and certain excluded income, such as foreign earned income. Subtract the adjustments to income on Schedule 1, lines 11 through 20, 23 and 25 (line 7). Student loan interest does not count here (IRC §86(b)(2)(A)).
Line 9 is your base amount: $25,000 for most filers and $32,000 on a joint return (IRC §86(c)(1)). At or below the base amount, none of your benefits are taxable.
Lines 10 to 15 apply the first tier, which runs up to the adjusted base amount: $34,000 for most filers and $44,000 on a joint return (IRC §86(c)(2)). Line 11 enters the gap between the two amounts: $9,000, or $12,000 on a joint return. There, half of each dollar above the base amount counts, but never more than half of your benefits (IRC §86(a)(1)). So up to 50 percent of your benefits can become taxable here. A married person who files separately and lived with the spouse at any time during the year has zero for both amounts (IRC §86(c)(1)(C), (2)(C)). The worksheet then skips lines 9 to 16 and counts 85 percent of line 8.
Lines 16 to 19 apply the second tier. Above the adjusted base amount, 85 percent of each extra dollar counts, on top of the first-tier amount. Line 18 caps the total at 85 percent of your benefits, and never more becomes taxable (IRC §86(a)(2)).
The trap sits in the second tier. Until the cap applies, each extra dollar of other income, such as a taxable withdrawal from a traditional IRA, adds that dollar plus 85 percent of it to your taxable income (IRC §86(a)(2)(A)(i)).
Does the 2025 tax law end tax on Social Security?
No. Public Law 119-21, the 2025 tax law, did not amend IRC §86, the section that taxes benefits. The U.S. Code’s list of every law that changed §86 ends with Public Law 117-2 of March 11, 2021. The base amounts and both tiers above still apply for 2025 and 2026. “No tax on Social Security” is not what the law did.
Instead, the law added a deduction for people 65 and older (IRC §151(d)(5)(C)). You can deduct $6,000 if you reach 65 before the year ends, and a joint return gets another $6,000 if your spouse does too. Each $6,000 shrinks by 6 percent of income above $75,000, or $150,000 on a joint return. The income here is your adjusted gross income plus certain excluded income, such as foreign earned income. The deduction covers tax years that begin before January 1, 2029. Each person needs a Social Security number valid for employment, and a married couple must file jointly.
The deduction depends on your age, not your benefits, and it leaves the taxable part of your benefits unchanged. IRC §62(a) does not list it among the deductions that figure adjusted gross income, and Worksheet 1 never asks for it. So this calculator leaves it out. The standard deduction calculator page explains it, though that calculator does not add it in either.
Common Questions
How much of my Social Security is taxable?
Between 0% and 85%, depending on your provisional income: your other income, plus tax-exempt interest, plus half of your benefits. At or below your base amount ($25,000 single, $32,000 married filing jointly), none is taxable. Above the adjusted base amount ($34,000 single, $44,000 joint), up to 85% is taxable. Enter your numbers above to see each step (IRC §86).
Do the Social Security taxation thresholds change every year?
No. IRC §86(c) names $25,000, $32,000, $34,000, and $44,000 as fixed amounts, and the section contains no inflation adjustment. We read the full text on 2026-09-20 and found none.
What is provisional income?
Provisional income is your adjusted gross income without the Social Security benefits, plus tax-exempt interest, plus half of your Social Security benefits. IRC §86(b) defines it, and line 8 of Pub. 915 Worksheet 1 computes it.
Are Tier 1 railroad retirement benefits taxed the same way?
Yes. IRC §86(d)(1) treats a Tier 1 railroad retirement benefit as a social security benefit. Add Box 5 of your Form RRB-1099 to Box 5 of any Form SSA-1099 and enter the total.
Why is my filing status “married filing separately” so costly?
If you file separately and lived with your spouse at any time during the year, your base amount is $0. Up to 85% of your benefits become taxable from the first dollar of income. If you lived apart from your spouse all year, the single amounts apply (IRC §86(c)(1)(C)).
Does this calculator handle a lump-sum payment for an earlier year?
No. If a payment covers an earlier year, IRC §86(e) and Pub. 915 Worksheets 2 through 4 may lower your taxable amount, and you elect that on Form 1040 line 6c. This calculator computes the standard Worksheet 1 result only.
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More practitioner writing from Forrest Baumhover, CFP®, EA at The Federal Tax Desk on Substack.
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