Hobby vs business
A "trade or business" requires regular, continuous activity engaged in for profit. A hobby is sporadic and primarily for personal enjoyment. The IRS lists nine factors (Reg. 1.183-2) including manner of carrying on, expertise, time and effort, expectation of appreciation, success in similar activities, history of income/loss, financial status, and personal pleasure. A profit motive is the central question.
Why it matters
Business income goes on Schedule C with deductible expenses and SE tax. Hobby income goes on Schedule 1 line 8 with NO deductions (TCJA eliminated hobby deductions through 2025). A hobby loss is not deductible — period.
Three-of-five-years presumption
A presumption of profit motive applies if the activity produced a profit in three of the last five years. Failing the test does not automatically make it a hobby — the nine factors still control — but it shifts the burden of proof to the taxpayer.
When SE tax kicks in
Schedule SE applies if net earnings from self-employment are $400 or more. Below $400, no SE tax — but Schedule C still applies (and gross receipts must be reported). Income above $400 requires the full SE-tax computation regardless of how small.
Common side-hustle deductions
Mileage to client sites, home office, internet, phone, supplies, courses and books related to the side gig, software subscriptions, marketing costs, payment processor fees. Even small amounts add up — and they reduce both income tax and SE tax.
Common mistakes worth avoiding
The recurring mistakes filers make on this topic cluster in three patterns: (1) optimizing for current-year tax at the expense of multi-year tax, (2) treating the choice as binary when the IRS framework actually allows nuance (partial elections, hybrid methods, year-by-year reassessments), and (3) deferring the analysis until the return is due rather than running it during the year when the result can still influence behavior. A short annual review — even thirty minutes — catches all three failure modes and replaces vague intuition with documented reasoning.
When to bring in a professional
DIY tax software handles most small-business returns competently, but a handful of situations reliably justify a CPA or enrolled agent: an entity formation or election, a multi-state filing situation, a significant fixed-asset purchase that triggers Section 179 or bonus depreciation modeling, a retirement-plan setup, an IRS notice or examination, and the year of an entity sale. Outside those situations, software plus an annual half-day of personal review produces a defensible return. The cheapest professional engagement is a one-hour consultation rather than a full-service tax-prep relationship.