Income and Assets · Adjustments to Income

Self-employment tax

Two provisions each take half of something, and they do entirely different jobs. IRC § 1402(a)(12) shrinks the base before the tax is computed, so the tax itself is smaller. IRC § 164(f) then allows a deduction against income for half the tax that results. Neither applies to the additional hospital insurance tax, which sits outside both. Getting the two confused produces a wrong answer in both directions at once.

The rule

Three rates, in one section. The tax on self-employment income is 12.4 percent for old-age, survivors and disability insurance (IRC § 1401(a)), plus 2.9 percent for hospital insurance (§ 1401(b)(1)), plus an additional 0.9 percent on self-employment income above a threshold (§ 1401(b)(2)(A)).

The additional tax has its own thresholds, and they do not move. They differ by filing status (IRC § 1401(b)(2)(A)(i)–(iii)) and are reduced, but not below zero, by wages taken into account for the corresponding FICA tax (§ 1401(b)(2)(B)). None of the three carries an inflation adjustment; the amounts are in the table below.

Only the first component has a ceiling. Self-employment income does not include, for the § 1401(a) tax, net earnings in excess of the contribution and benefit base under section 230 of the Social Security Act for the calendar year in which the taxable year begins, minus wages paid to the individual during the year (IRC § 1402(b)(1)). The hospital insurance components have no ceiling at all.

And a floor below which nothing is taxed. Self-employment income does not include net earnings from self-employment where those earnings for the year fall below a small statutory floor (IRC § 1402(b)(2)).

Net earnings, and four exclusions. Net earnings from self-employment are gross income from any trade or business carried on by the individual, less the deductions attributable to it, plus the distributive share of income or loss described in § 702(a)(8) from a partnership of which the individual is a member (IRC § 1402(a)). From that are excluded: rentals from real estate and from personal property leased with it, unless received in the course of a trade or business as a real estate dealer, and subject to a material-participation exception for farm arrangements (§ 1402(a)(1)); dividends and interest, unless received as a dealer in stocks or securities (§ 1402(a)(2)); and gain or loss treated as from a capital asset, or from property that is neither inventory nor held primarily for sale to customers (§ 1402(a)(3)).

A limited partner’s share is out. The distributive share of any item of income or loss of a limited partner, as such, is excluded — other than guaranteed payments under § 707(c) for services actually rendered, to the extent established to be remuneration for those services (IRC § 1402(a)(13)).

The first halving: the base shrinks. In lieu of the § 164(f) deduction, net earnings are reduced by the product of those earnings and one-half of the sum of the § 1401(a) and (b)(1) rates, determined without regard to the additional rate under § 1401(b)(2) (IRC § 1402(a)(12)). Half of 15.3 percent is 7.65 percent, so the base is 92.35 percent of net earnings.

The second halving: an income tax deduction. In addition to the taxes described in § 164(a), a deduction is allowed for one-half of the taxes imposed by § 1401 — other than the additional tax under § 1401(b)(2) — and the deduction is treated as attributable to a trade or business not consisting of services as an employee (IRC § 164(f)(1), (2)). It reduces income tax, not self-employment tax.

Employees and officeholders are not self-employed. A trade or business has its § 162 meaning, except that it does not include the functions of a public office — other than certain State fee-basis positions — or the performance of service as an employee, subject to narrow exceptions (IRC § 1402(c)(1), (2)).

Current figures

How it works in practice

Work the computation in the statutory order and the two halvings stop competing. Start with net earnings from the business. Apply the § 1402(a)(12) reduction to get the base — 92.35 percent of net earnings. Apply 12.4 percent to so much of that base as fits under the ceiling after subtracting any wages, and 2.9 percent to all of it. Add the additional 0.9 percent on the excess over the threshold. Then, and only then, take half of the first two components as a § 164(f) deduction in computing adjusted gross income.

The wage coordination in § 1402(b)(1) matters for anyone with both a job and a business. Wages consume the ceiling first, so an employee earning above the base owes no old-age component on the side business at all — but still owes the full 2.9 percent, and the additional 0.9 percent threshold in § 1401(b)(2)(B) is reduced by those same wages, so the surtax bites sooner rather than later.

The exclusions are where classification arguments live. Rental income is out unless the taxpayer is a real estate dealer; portfolio income is out unless the taxpayer is a securities dealer; gain on the sale of business equipment is out because § 1402(a)(3)(C) excludes property that is neither inventory nor held primarily for sale. A sole proprietor selling their delivery van has a § 1231 gain and no self-employment tax on it.

How this has changed

The additional hospital insurance tax was bolted on in 2013 and does not behave like the rest of the section. Section 1401(b)(2) applies only to taxable years beginning after 31 December 2012, has its own thresholds, is excluded from the § 1402(a)(12) base reduction and from the § 164(f) deduction, and — like the § 1411 thresholds and the § 86 base amounts — carries no inflation adjustment. Three unindexed threshold sets now sit on the same return at the same two figures, and none of them moves.

The limited partner exclusion has not changed and its boundary is contested. Section 1402(a)(13) excludes a limited partner’s distributive share “as such”, and the words are doing the work: the exclusion is directed at the passive character of the interest, not at the label in the partnership agreement. Guaranteed payments for services actually rendered are carved back in.

The ceiling is set outside the Code. Section 1402(b)(1) points at the contribution and benefit base under section 230 of the Social Security Act, which is announced annually by the Social Security Administration rather than by the IRS. Any tax table of it is a secondary report of a figure that lives elsewhere, so check the year it is stated for: the amount in the current figures table above is the 2026 base as the IRS reports it.

What has not changed is the structure of the two halvings, in place since 1990, and it remains the most reliable source of error on this topic — including in published material, which frequently describes the 92.35 percent figure as “the deduction for half the self-employment tax” when it is a separate provision doing a separate job.

Exam focus

Expect the order of the computation: reduce the base, then apply the rates, then take the deduction.

Expect wages in the facts, testing whether you know they consume the ceiling and shrink the additional-tax threshold.

Expect a rental or a gain on business property, both of which are excluded from net earnings.

Expect the statutory floor, which is measured on net earnings and is not prorated.

Check yourself

1. A sole proprietor has 50,000 dollars of net earnings and no wages. What amount do the rates apply to?

Answer: 46,175 dollars. IRC § 1402(a)(12) reduces net earnings by the product of those earnings and one-half of the combined § 1401(a) and (b)(1) rates — 7.65 percent — leaving 92.35 percent of 50,000.

2. What is the income tax deduction, and which taxes does it cover?

Answer: One-half of the taxes imposed by IRC § 1401 other than the additional tax under § 1401(b)(2), allowed by § 164(f)(1) in computing adjusted gross income and treated as attributable to a trade or business not consisting of services as an employee.

3. A taxpayer’s wages already exceed the contribution and benefit base. Do they owe any self-employment tax on a side business?

Answer: Yes — the hospital insurance components. IRC § 1402(b)(1) removes only the § 1401(a) tax to the extent wages have consumed the base; the 2.9 percent tax has no ceiling and the additional 0.9 percent may apply, with its threshold reduced by those wages under § 1401(b)(2)(B).

4. A taxpayer nets 380 dollars from a small side activity. What is owed?

Answer: Nothing. IRC § 1402(b)(2) excludes net earnings from self-employment where they fall below the statutory floor of 400 dollars for the taxable year.

5. A sole proprietor sells a delivery van used in the business at a gain. Is the gain subject to self-employment tax?

Answer: No. IRC § 1402(a)(3)(C) excludes gain from the disposition of property that is neither inventory nor held primarily for sale to customers in the ordinary course of the trade or business.