Above-the-line deduction
The self-employed health insurance deduction goes on Schedule 1 line 17, reducing adjusted gross income. Unlike the medical-expense itemized deduction (limited to amounts above 7.5% of AGI), this above-the-line deduction is dollar-for-dollar from the first premium paid.
Eligibility
You can claim the deduction if you had a net profit from self-employment, were a partner with self-employment income, or were a more-than-2% S-corp shareholder whose health insurance premiums were paid by the corporation and reported on the W-2 in Box 1 (but excluded from Boxes 3 and 5).
Limitation
The deduction is limited to the net earnings from the trade or business under which the insurance plan is established. If you have no net profit from that business, you cannot use this deduction (although you may still itemize the medical expense above 7.5% of AGI on Schedule A).
Subsidy interaction
If you receive an advance premium tax credit (APTC) on a marketplace plan, the deduction equals premiums paid minus the APTC. The math is iterative because the deduction affects AGI which affects APTC eligibility — software handles the loop, but it is helpful to understand why the deductible amount differs from total premiums.
Family coverage
Premiums paid for the spouse, dependents, and any non-dependent child under age 27 (regardless of whether they are claimed on your return) are eligible for the deduction.
Where this fits in the larger Schedule C picture
Schedule C has more than two dozen named expense lines plus an "Other expenses" catch-all. For most small businesses, four or five lines drive the bulk of the deduction total — vehicle, home office, depreciation, contract labor or wages, and supplies — and the remaining lines individually contribute small amounts that nevertheless add up. Treating each named line as a recurring decision rather than an afterthought, and revisiting the categories each January, often surfaces $2,000–$5,000 in additional legitimate deductions that a less disciplined process would have missed entirely.
Documentation that survives an exam
An IRS examination of this deduction will request three things: proof of payment (bank or card statement), proof of the underlying transaction (invoice or receipt), and proof of business purpose (a contemporaneous note or calendar entry). The first two are usually trivial to produce; the third is where most filers fall short. Capturing business purpose at the moment of the expense — a one-line note in your bookkeeping software or a category and memo on the receipt-capture app — converts a generic charge into a documented deduction that will withstand scrutiny three to six years later when memory has faded.