Many retirees are surprised to learn that Social Security benefits can be taxable. Whether yours are -- and how much -- depends on a figure called "combined income," which the IRS uses to determine how much of your benefit to include in taxable income. The thresholds have not been adjusted for inflation since 1984 and 1993, which means more retirees cross them each year as benefit amounts rise.
What Is "Combined Income"?
Combined income is the IRS's specific formula for measuring total income for Social Security taxation purposes:
Combined Income = Adjusted Gross Income + Nontaxable Interest + 50% of Social Security Benefits
Note: tax-exempt municipal bond interest is included even though it is not normally in AGI.
The Three Tiers: 0%, 50%, and 85%
| Filing Status | Combined Income | Taxable Portion |
|---|---|---|
| Single / Head of Household | Below $25,000 | 0% |
| Single / Head of Household | $25,000 -- $34,000 | Up to 50% |
| Single / Head of Household | Above $34,000 | Up to 85% |
| Married Filing Jointly | Below $32,000 | 0% |
| Married Filing Jointly | $32,000 -- $44,000 | Up to 50% |
| Married Filing Jointly | Above $44,000 | Up to 85% |
A Worked Example
You are single, receive $24,000 in Social Security benefits, and have $18,000 in IRA withdrawals and $2,000 in interest income.
- AGI: $20,000
- 50% of Social Security: $12,000
- Combined income: $32,000 -- in the 50% tier
- Taxable portion: lesser of 50% of benefits ($12,000) or 50% of the amount over $25,000 ($3,500)
- $3,500 of your Social Security is taxable
Planning Strategies
- Roth conversions before claiming Social Security reduce future RMDs and combined income
- Qualified Charitable Distributions (QCDs) satisfy RMDs without increasing AGI
- HSA spending for medical expenses avoids adding to AGI
State Taxes on Social Security
Most states do not tax Social Security benefits, but 10 states currently do to varying degrees. Check your state income tax calculator for state-specific information.
Source
IRS Publication 915 (Social Security and Equivalent Railroad Retirement Benefits); Social Security Administration OASDI Fact Sheet 2026.