When a Retirement Activity Becomes a Business
Plenty of people leave work and start doing something that brings in money — woodwork, consulting a few days a month, restoring furniture, selling at markets. The income is taxable regardless. What turns on the classification is the expenses: a business deducts them and a hobby does not, and the difference on a modest activity can exceed the profit itself.
- Income is taxable either way:: Money from an activity is reportable whether it is a hobby or a business.
- Only a business deducts expenses:: Hobby expenses are generally not deductible for individuals, so tax falls on gross receipts.
- A business owes self-employment tax:: Both halves of Social Security and Medicare apply to the profit.
- It is decided by facts:: The manner of operation, expertise, time spent, and history of profit all count.
Where the AI summary above gets this wrong
"Deduct the costs of your side activity against the income it produces."
That's surface-true. Here's what it misses:
- Hobby expenses are generally not deductible at all — For individuals, hobby income is reported and the expenses of producing it are not offset against it. That means tax on gross receipts. A craft activity turning over $9,000 with $7,500 of materials produces $1,500 of real profit and is taxed on the full $9,000 if it is a hobby.
- The classification is not a choice — It follows from the facts: whether the activity is carried on in a businesslike manner, the expertise brought to it, the time and effort devoted, whether losses are in a start-up phase, and the history of profit. Deciding to call something a business does not make it one.
- Business treatment brings a tax as well as a deduction — Net profit from a business is subject to self-employment tax — both halves of Social Security and Medicare — on top of income tax. For an activity with slim margins, business treatment can produce a larger total bill than hobby treatment, and the comparison is worth running rather than assuming.
01 What separates the two
The central question is whether the activity is carried on with a genuine intention to make a profit. That is judged from conduct rather than from stated intent, using a set of factors applied together.
They include whether the activity is conducted in a businesslike manner with proper records, the expertise of the person carrying it on, the time and effort devoted to it, whether the assets are expected to appreciate, past success in similar activities, the history of income and losses, and the extent of any personal pleasure derived.
No single factor decides it. An activity that has produced a profit in several recent years is on much firmer ground, and one that has never produced one and is plainly enjoyable is on weaker ground however it is labelled.
Source: Paying taxes on hobby activities
02 What each treatment means
As a hobby, the income is reported and the expenses are generally not deductible for individuals. Tax falls on what came in, without regard to what it cost to produce.
As a business, ordinary and necessary expenses are deducted and tax falls on the profit. Losses can offset other income, subject to limits, and a retirement plan for the self-employed becomes available — the comparison set out in SEP versus solo 401(k) only applies to genuine business income.
The offsetting cost is self-employment tax on the profit, which for a modest activity can exceed the income tax saved by deducting the expenses. Business treatment is better for an activity with real margins and not automatically better for one without.
Shows: the difference between being taxed on gross receipts as a hobby and on net profit as a business, at the rate you enter. Ignores: self-employment tax, which a business pays and a hobby does not, state tax, and the fact that the classification follows the facts rather than being chosen.
Source: Business activities
03 Getting the treatment you are entitled to
If the activity genuinely is a business, the way to be treated as one is to operate like one. Separate bank account. Records of income and expenses kept contemporaneously. A written sense of how it is meant to become profitable, and changes made when it does not.
Those things are not a formality. They are the evidence the factors are assessed against, and a person with three years of accounts and a separate account is in a very different position from one with a shoebox.
If it genuinely is a hobby, the useful response is different: keep the receipts anyway, since costs that are part of the basis of goods sold are treated differently from ordinary expenses, and consider whether the activity's scale makes it worth restructuring at all. Plenty of worthwhile retirement activities should stay hobbies, and understanding the tax is different from changing it — the same distinction that runs through the rules on working in retirement generally.
Source: Publication 535
The instinct is to call everything a business because businesses deduct things, and that instinct is frequently wrong on the arithmetic as well as the law. Run the comparison first: income tax on receipts as a hobby, against income tax on profit plus self-employment tax as a business. For a lot of pleasant retirement activities, hobby treatment costs less and asks for nothing. If it really is a business, then operate like one from day one — separate account, real records — because that is what the classification is assessed on.
FAQ
Can I deduct expenses from a hobby?
Generally not, for individuals. Hobby income is reported and the expenses of producing it are not offset against it, which means tax falls on gross receipts.
How do I know if my activity is a business?
It turns on whether it is carried on with a genuine profit motive, judged from conduct: businesslike operation, records, expertise, time devoted, and the history of profit. It is not a label you choose.
Is business treatment always better?
No. A business deducts expenses but also owes self-employment tax on the profit. For an activity with thin margins, the total bill can be higher, so the comparison is worth running.
Sources
Regulator references
- Paying taxes on hobby activities · Internal Revenue Service · 2026The factors that distinguish a hobby from a business and how hobby income is treated.Last verified: 2026-09-07
- Business activities · Internal Revenue Service · 2026What constitutes carrying on a trade or business.Last verified: 2026-09-07
- Publication 535 · Internal Revenue Service · 2026Which expenses are deductible when an activity is a business.Last verified: 2026-09-07
Calculator unit tests · the assertions this page's worked example is checked against, and their last result
Changelog
- 2026-09-07 — initial publish (new format)
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Jordan Reeves
Founder of Talk Through Wealth. A software engineer for over a decade before turning to retirement planning, Jordan built the projection engine after watching family members get fragmented, country-by-country advice that never reconciled. He writes about retirement the way the engine computes it: month-by-month, lifetime-long, and skeptical of any rule of thumb that hasn't been run through the math.