How does self-employment income affect ACA health insurance subsidies?

Marketplace premium subsidies are tied to your estimated annual household income, so your self-employment earnings directly determine how much help you get — and because that income is variable, estimating it well matters. Subsidies are based on a percentage of the federal poverty level; lower income generally means a larger subsidy. When you apply, you project your expected income for the year, and at tax time it's reconciled: if you earned more than estimated, you may repay some subsidy, and if less, you may get more back. A useful lever is that contributing to a Solo 401(k) or SEP-IRA and deducting self-employed health insurance lowers your adjusted gross income, which can increase your subsidy. Update the marketplace if your income changes significantly mid-year to avoid a surprise at filing. Estimate carefully but conservatively, since overestimating costs you upfront and underestimating risks a repayment.