Working out of the spare room? What the home office deduction actually requires
title:Working out of the spare room? What the home office deduction actually requiresauthor:Marguerite Vasquezpublished:2025-11-06section:Personal Financewords:807read:3 min
The test is narrower than most people assume and the paperwork is lighter, and the local rules that surround it are a separate question entirely.
Two tests decide whether a room qualifies, and both are stricter than the version people repeat to each other. The room has to be used regularly for business, and it has to be used exclusively for it.
Exclusively means what it sounds like. A desk in the corner of a bedroom does not qualify because the bedroom is a bedroom; a converted spare room with a desk, a filing cabinet and no guest bed does.
Where the exclusivity test bites
The common failure is not deliberate. It is the treadmill in the corner, the closet still holding out-of-season clothes, the room that becomes a guest room twice a year at the holidays. Each of those is personal use of the space, and personal use of the space is the thing the test is looking for.
The workaround is usually physical rather than clever. Move the treadmill. Empty the closet. If the room genuinely doubles as a guest room, measure and claim only the portion that does not, provided that portion is identifiable and used for nothing else.
A partition, or simply a clearly defined area, is easier to defend than an argument about how often the sofa bed comes out.
There is a second route for people who are not employees: the space has to be the principal place of business, or a place where clients are regularly met. A contractor who does the work at customer sites but does all the scheduling, invoicing and ordering from the spare room generally satisfies this, because administrative work performed nowhere else counts.
Two ways to calculate it
| Simplified | Actual expenses | |
|---|---|---|
| What you track | Square footage of the space | Every household cost, plus the business percentage |
| Records needed | A measurement | Utility bills, insurance, repairs, mortgage interest or rent, property tax |
| Usually larger for | Small spaces, renters with low costs | Larger spaces, high utility or rent costs |
| Effect at sale | No depreciation to account for | Depreciation claimed has to be reckoned with later |
The choice is not permanent, which surprises people. It can be made year by year. The sensible approach is to compute both once, see how far apart they are, and only keep the heavier records if the gap justifies the effort.
If actual expenses beat the simplified method by a small margin, the simplified method probably wins anyway on the hours it saves. The instructions for both methods are published by the IRS, which administers the deduction.
The local rules nobody mentions
The deduction is a federal question. Whether you are allowed to run the business from that room at all is a local one, and the two are decided by entirely different offices that never speak to each other.
Most cities and counties have a home occupation ordinance. It typically restricts signage, client foot traffic, employees on site, deliveries by commercial vehicle, and the storage of certain materials. A consultant working alone from a laptop is invisible to it.
A cabinet maker with a dust collector in the garage and a truck out front is not, and the complaint that starts the process is almost always a neighbor rather than an inspector on patrol.
Many jurisdictions also require a home occupation permit or a business license even for the invisible cases. It is usually inexpensive and usually annual. Where it matters is in the paperwork chain: some insurers want to see it, and having filed for it is useful evidence that the room is what you say it is.
Then there is the homeowners association, if there is one. Covenants sit outside the city code entirely and can be stricter. They are enforced by a board rather than by an inspector, which changes the character of any dispute but not the outcome.
What it does to the property side
Two effects are worth knowing before you claim anything. Depreciation taken on the business portion of a home you own has to be accounted for when the house is sold, which reduces the appeal of the actual expense method for someone likely to move soon.
And the assessed value your county uses for property tax is generally unaffected by a deduction claimed on a federal return, since the assessor works from its own records and its own schedule.
People occasionally conflate the two and decide against claiming anything for fear of a reassessment. That fear is usually misplaced, but it is worth a call to the county assessor's office if the business involves a structural change, because a permitted conversion is a different matter from a desk in an existing room.
Measure the room, photograph it as it is actually used, check the city's home occupation rules once, and keep the measurement with the tax file. The deduction is small in any single year and completely uncontroversial when the room really is what you say it is.