Taxation of Social Security benefits

Since the passage of the 1983 Amendments to the Social Security Act Social Security benefits are subject to taxation.

The amount of Social Security income which is taxable depends on your taxable income. Most high-income retirees will have 85% of Social Security benefits taxable. For lower-income retirees, less than 85% will be taxable, but many retirees in a 12% tax bracket will face a marginal tax rate much higher than 12%. Social security benefits are also taxable in some states (see Figure 1.)

For social security taxes imposed on earned wages, see the Payroll tax article.

The formula
The full rules are in IRS Publication 915. This simplification covers most cases; there are special rules if you contribute to a Traditional IRA, receive retroactive payments for prior years, or file forms to exempt other income from taxation.

The relevant income for Social Security taxation includes all items which are normally part of your adjusted gross income, plus tax-exempt interest income, plus 50% of your Social Security benefits. (Historically, the 50% represents the fact that half of your Social Security contributions were made by your employer and thus not taxed.)

There are two relevant base amounts; unlike most income limits in the tax code, they are not adjusted for inflation. The lower base is $25,000 if you are single, $32,000 if married filing jointly. The upper base is $34,000 if you are single, $44,000 if married filing jointly.

If your relevant income is below the lower base, none of your benefits are taxable. For every $1 of relevant income between the lower and upper bases, 50 cents of your Social Security benefits become taxable, up to 50% of your total benefits. For every $1 of relevant income above the upper bases, 85 cents of your Social Security benefits become taxable, up to a total taxable amount of 85% of your benefits.

Examples
The examples below are based on tax numbers for 2019. They illustrate how tax brackets and Social Security taxation interact, creating a 22.2% marginal tax rate for most taxpayers in the 12% tax bracket, and a 40.7% marginal tax rate for

- single taxpayers 65 and older with SS benefits above $18,237; at that SS, the marginal tax rate begins at ordinary income of $37,824;

- married taxpayers 65 and older with SS benefits above $51,118; at that SS, the marginal tax rate begins at ordinary income above $62,500.

Single taxpayers:

If you are single and receive $20,000 in Social Security benefits:
 * None of your benefits are taxable if your other income is less than $15,000.
 * For every dollar between $15,000 and $24,000, an additional 50 cents becomes taxable.
 * For every dollar over $24,000, an additional 85 cents becomes taxable, up to a total other income of $38,706, which makes the maximum $17,000 taxable.

The table below assumes that you take the standard deduction ($13,850 for a taxpayer over 65)

In graphical form, assuming the non-SS income comes from tIRA withdrawals,



Married taxpayers:

If you are a married couple and receive $40,000 in Social Security benefits:
 * None of your benefits are taxable if your other income is less than $12,000.
 * For every dollar between $12,000 and $24,000, an additional 50 cents becomes taxable.
 * For every dollar over $24,000, an additional 85 cents becomes taxable, up to a total other income of $56,941, which makes the maximum $34,000 taxable.

The table below assumes that you take the standard deduction ($27,000 for a married couple over 65).

In graphical form, assuming the non-SS income comes from tIRA withdrawals,



There is no 40.7% rate in this situation because the example couple reaches the maximum taxable benefit amount well before reaching the 22% tax bracket.

Heat map representation
Plotting marginal tax rates as a function of Social Security income (horizontal axis) and non-Social Security income (vertical access) gives the following "heat map" style plots.





The central point on each plot above which 40.7% marginal rates become possible can be calculated directly the formulas that describe taxation of Social Security, described above. As of 2019, these values are:

Taxpayers earning less Social Security income than these values are possibly affected by the 22.2% bump. As a function of annual Social Security benefit (SS), the 22.2% bump begins and ends at the following levels of income from other sources:

Taxpayers earning more Social Security income than the above values are possibly affected by the 40.7% bump. As a function of annual Social Security benefit (SS), the 40.7% bump begins and ends at the following levels of income from other sources:

See the appendix below for a derivation of these formulas.

Examples
A single taxpayer receiving $20,000 of Social Security benefits would be possibly affected by the 40.7% bump because the amount is more than $18,236. The 40.7% bump begins at $37,420 ($42,014 - 0.2297 * $20,000) and ends at $38,706 ($28,706 + 0.5 * $20,000). These values agree with the above charts within $1.

Married taxpayers receiving $40,000 of Social Security benefits would be possibly affected by the 22.2% bump, but not the 40.7% bump, because the amount is less than $51,118. The 22.2% bump begins at $32,866 ($74,243 - 0.2297 * $40,000) and ends at $56,941 ($36,941 + 0.5 * $40,000). These values also agree with the above charts within $1.

State taxation
While most states do not tax social security benefits (shaded blue in figure; along with green shaded states which do not impose income tax), six states tax benefits to the extent they are taxed at the federal level (shaded lavender), while eight states exempt social security benefits from taxation subject to limits (shaded yellow).

The states that tax benefits to the extent they are taxed at the federal level include:
 * Minnesota
 * Nebraska
 * North Dakota
 * Rhode Island
 * Vermont
 * West Virginia

The states that tax social security benefits subject to limits include:
 * Colorado: If a household meets certain age requirements qualifying retirement income can be excluded from income if it is taxable under federal income tax.
 * Connecticut: Allows taxpayers to totally exempt social security from state income tax if income is less than $60,000 (joint filers).
 * Iowa: In 2013 exempts a certain portion of benefits from income tax. In 2014 the exemption will increase to 100%.
 * Kansas: Exempts social security benefits from state taxation if federal adjusted income is less than $75,000.
 * Missouri: Allows taxpayers with adjusted gross income of less than $100,000 (joint filers) to deduct all social security benefits from income.
 * Montana: Some social security benefits may be taxable (state advises filling out a worksheet); in general if total income is below $32,000 joint filers, benefits will not be subject to tax.
 * New Mexico : Benefits are taxable, but a person can qualify for an exemption if he or she is 65 years of age or older.
 * Utah: If a household meets certain age requirements qualifying retirement income can be offset by credit, which is phased out once income exceeds a certain level.

Appendix: derivation of tax rate boundaries
Variables are defined as follows:

$$ \begin{align} SS & = \text{Social Security income} \\ OI & = \text{other income} \\ BT & = \text{bracket threshold} \\ SD & = \text{standard deduction} \\ LB & = \text{lower base} \\ UB & = \text{upper base} \\ RI & = \text{relevant income} = 0.5 \cdot SS + OI \\ \end{align} $$

Point above which 40.7% marginal rate is possible
The point above which 40.7% marginal tax rates is possible is when total taxable income is at the 22% tax bracket threshold and the maximum 85% of Social Security benefits are taxable. It is the combination of $$SS$$ and $$OI$$ that satisfies these two equations:

$$0.85 \cdot SS + OI - SD = BT$$

$$0.5 \cdot (UB - LB) + 0.85 \cdot (RI - UB) = 0.85 \cdot SS$$

The solutions are:

$$SS^{*} = \dfrac{0.5 \cdot (UB - LB) + 0.85 \cdot (BT + SD - UB)}{1.1475}$$

$$OI^{*} = BT + SD - 0.85 \cdot SS^{*}$$

For 2019, for single filers and assuming a $13,850 standard deduction, the point is:

$$(SS^{*},\ OI^{*}) = ($18,236.38,\ $37,824.07)$$

For married joint filers and assuming a $27,000 standard deduction, the point is:

$$(SS^{*},\ OI^{*}) = ($51,117.65,\ $62,500.00)$$

22.2% bump begins
For single filers, the 22.2% bump begins in the middle of the 12% bracket when Social Security taxation begins to be taxed at an 85% marginal rate. This occurs when:

$$0.5 \cdot SS + OI = UB$$

Substituting $34,000 for UB gives:

$$OI = $34,000 - 0.5 \cdot SS$$

For married filers, the 22.2% bump begins at the boundary between the 10% and 12% brackets. The line is defined by the solution to these equations:

$$0.5 \cdot (UB - LB) + 0.85 \cdot (RI - UB) = p \cdot SS$$

$$OI + p \cdot SS = BT + SD$$

where $$p$$ is the percentage of Social Security income that is taxable. The solution to this set of equations is:

$$OI = \dfrac{BT + SD + 0.85 \cdot UB - 0.5 \cdot (UB-LB)}{1.85} - \dfrac{0.425 \cdot SS}{1.85}$$

Substituting $19,400 for BT, $27,000 for SD, $44,000 for UB, and $32,000 for LB gives:

$$OI = $42,054.05 - 0.22973 \cdot SS$$

22.2% bump ends
The 22.2% bump ends when the maximum of 85% of Social Security benefits becomes taxable. This occurs when:

$$0.5 \cdot (UB - LB) + 0.85 \cdot (RI - UB) = 0.85 \cdot SS$$

Solving for OI gives:

$$OI = \left ( UB - \frac{0.5}{0.85} \cdot (UB - LB) \right ) + 0.5 \cdot SS$$

For single filers, substitute $34,000 for UB and $25,000 for LB and the result is:

$$OI = $28,705.88 + 0.5 \cdot SS$$

For married joint filers, substitute $44,000 for UB and $32,000 for LB and the result is:

$$OI = $36,941.18 + 0.5 \cdot SS$$

40.7% bump begins
For both single and married filers, the 40.7% bump begins at the boundary of the 22% bracket. The formula is the same as for the beginning of the 22.2% bump for married filers, but with a different bracket threshold:

$$OI = \dfrac{BT + SD + 0.85 \cdot UB - 0.5 \cdot (UB-LB)}{1.85} - \dfrac{0.425 \cdot SS}{1.85}$$

For single filers, substituting $39,475 for BT, $13,850 for SD, $34,000 for UB, and $25,000 for LB gives:

$$OI = $42,013.51 - 0.22973 \cdot SS$$

For married filers, substituting $78,950 for BT, $27,000 for SD, $44,000 for UB, and $32,000 for LB gives:

$$OI = $74,243.24 - 0.22973 \cdot SS$$

40.7% bump ends
The line where the 40.7% bump ends is the same as where the 22.2% bump ends. The only difference is whether the boundary is above or below $$SS^{*}$$. For single filers, the formula is:

$$OI = $28,705.88 + 0.5 \cdot SS$$

For married joint filers, the result is:

$$OI = $36,941.18 + 0.5 \cdot SS$$