The Home Office Deduction (Section 280A)

How it works

I have a longer walkthrough of the simplified-versus-actual arithmetic in my home office deduction guide. This page is the other half: where the position comes from in the law, who actually gets it, and where it falls apart on examination.

Section 280A(a) is a blanket rule against deducting anything tied to a dwelling unit used as a residence. The home office deduction exists only because Section 280A(c) carves a narrow exception out of that rule. Understood that way, the deduction is not a benefit Congress handed out. It converts a slice of otherwise personal, nondeductible housing cost, rent or mortgage interest, property tax, utilities, insurance, repairs, and depreciation, into a business expense, because that slice is tied to space genuinely used for the business.

What that conversion is worth depends entirely on who is claiming it. A Schedule C filer takes the deduction above the self-employment tax line, so it reduces both income tax and the 15.3% self-employment tax at once. An S corporation owner-employee gets none of that directly. The only route available runs through an accountable-plan reimbursement: the corporation deducts what it pays the owner, and the owner receives it with no W-2 wage attached and no FICA, because it was never wages in the first place.

The Florida piece

Florida has no individual income tax, so this is federal only from the start. The S corporation route does not add a state layer either: the reimbursement is deductible to the corporation and excluded from the owner's income under federal law, with neither event touching a Florida return. Florida shows up instead on the property side, covered under failure modes below.

Who this applies to

Two tests have to hold at the same time before any use category even matters.

• Regular use. The space has to be used for business on a continuing basis. Occasional or incidental use does not clear this bar.
• Exclusive use. The specific area has to be used only for business, with no personal use at all. A spare bedroom that doubles as a guest room fails this test regardless of how often it is actually used for work. There are two narrow statutory exceptions to exclusivity, for storing inventory or product samples where the home is the business's only fixed location, and for a licensed daycare facility. Neither is the common case for a service business.

Then one of three use categories has to be satisfied:

• Principal place of business, which includes a home used for the administrative or management side of the business, billing, scheduling, bookkeeping, when there is no other fixed location where substantial administrative or management work happens. Congress added this branch by statute in 1997, codifying the response to Commissioner v. Soliman, whose pre-1997 principal-place test prompted the fix. It is the branch that reaches someone who works on site for clients but does the billing, scheduling, and records at home.
• A place to meet clients or customers in the normal course of business.
• A separate structure not attached to the dwelling, used in connection with the business. Exclusive use still applies, but the principal-place test is relaxed.

Entity type decides who can even get in the door:

• Self-employed, Schedule C, or a single-member LLC is fully eligible for the direct deduction.
• A partner in a partnership may deduct it as an unreimbursed partner expense on Schedule E, if the partnership agreement requires the partner to bear the cost personally.
• An S corporation or C corporation owner-employee gets no personal deduction at all. Employee home office expense used to live in the miscellaneous itemized deductions subject to the old 2 percent of adjusted gross income floor, suspended for 2018 through 2025 under the Tax Cuts and Jobs Act. The One Big Beautiful Bill Act made that suspension permanent, now in Section 67(h). The accountable plan is not a workaround. It is the only route the law leaves open.

One more gate sits underneath all of this for the direct, self-employed deduction: it cannot exceed gross income from the business use of the home minus the business deductions unrelated to the home and the home office portion of mortgage interest and property tax, and it cannot create or enlarge a loss. This gross income limitation does not apply to the accountable-plan reimbursement, which is a business expense of the corporation rather than a personal deduction bounded by the owner's own numbers.

What it requires

For the self-employed, the choice between the two computation methods is made fresh every year and does not bind the following year.

• The simplified method pays a flat $5 per square foot of qualified business-use area, on a maximum of 300 square feet, for a $1,500 ceiling on the deduction. That rate has never been adjusted for inflation and is unchanged for 2025 and 2026. No depreciation is taken, so there is nothing to recapture later, and mortgage interest and property tax are still claimed in full on Schedule A rather than split. Any amount the gross income limitation disallows under the simplified method simply disappears; it does not carry forward, and a carryover built up under the actual method in an earlier year cannot be used in a simplified-method year.
• The actual-expense method requires Form 8829 and a business percentage, business square footage divided by total home square footage. Direct expenses, painting only the office, are fully deductible. Indirect expenses, the whole-home costs like utilities, insurance, and mortgage interest, are deductible only at the business percentage. Depreciation on the business portion of an owned home runs on a 39-year straight line as nonresidential real property. Unlike the simplified method, a disallowed excess under the gross income limitation carries forward to later years.

For an S corporation owner, the requirement is structural rather than computational: a written accountable plan has to exist, and it has to satisfy three conditions at once under the governing Treasury regulation. There has to be a business connection between the expense and the corporation's business. The owner has to substantiate the expense, the business percentage and the allocable share of the actual costs, within a reasonable time. And any advance paid in excess of what gets substantiated has to actually be returned. Miss any one of the three, and the reimbursements lose accountable-plan treatment and are recharacterized as wages, taxable and subject to withholding.

What the plan may never do is pay the owner rent for the space. A corporation renting an owner's home office is a different transaction with a much worse outcome, covered in the next section.

What you need to document

The paperwork is what decides whether either version of this survives contact with an examiner, and it has to exist as the year goes, not get assembled afterward from memory.

Proof the space is exclusive

Photographs and a floor plan showing the boundaries of the space and the absence of any personal furniture or use inside it. Exclusive use is the single most common trigger for a disallowance, which is what this evidence is built to answer.

The square footage math

The measurements behind the business percentage.

A written accountable plan, dated before any reimbursement

For an S corporation owner, the plan document itself, adopted before the first payment under it, not drafted afterward to describe what already happened.

Expense reports

A monthly or quarterly report showing the business-use square footage and the allocable share of real costs: mortgage interest, property tax, utilities, insurance, HOA, repairs, and depreciation if the home is owned.

A record of any overlapping use of the residence

If the same home is also used under the Augusta rule, the rental days claimed there and the home office space claimed here need to be tracked separately, so the same square footage or the same days are never counted toward both positions at once.

Where it goes wrong

Exclusive use is the most common reason this gets disallowed. A room with a television, a guest bed, or a treadmill in it fails the test no matter how much genuine work happens there, because the statute asks about the space, not about the balance of activity inside it. The Tax Court has been consistently unforgiving on this point.

Hamacher v. Commissioner is worth knowing here, though not for exclusive use, which is the reason it usually gets cited. It did not turn on personal items in the room. The taxpayer ran two separate business activities out of one home office, and the court held the space has to satisfy Section 280A(c)(1) as to each activity separately. His employee activity then failed on the convenience-of-the-employer clause, because the employer had given him a suitable office he could reach at any time. Anyone splitting a home office between a job and a side business is standing in that fact pattern.

Losing the "no other fixed location" test is the other way the administrative-and-management route fails. If the business also rents outside office space and the administrative work moves there, the principal-place argument for the home office is gone, even if the space itself never changes.

The self-rental trap is the single most common error an S corporation owner makes here. It happens when the corporation pays the owner rent for the home office instead of using an accountable plan, usually because rent sounds like the natural word for it. Section 280A(c)(6) responds by disallowing the owner's offsetting deductions against that rental income, so the rent becomes fully taxable on Schedule E with nothing to net against it. I go through this failure in detail in the self-rental trap, but in short, the accountable plan and the rent arrangement are not two versions of the same idea. One produces a clean deduction and a tax-free receipt; the other produces ordinary taxable income with the expense side stripped away.

An accountable plan that is accountable in name only gets recharacterized as wages if it is missing the written plan, the substantiation, or the return of any excess advance. Recharacterized wages are includible in income and subject to withholding, Social Security, and Medicare, on top of losing the tax-free treatment it was built for.

Depreciation recapture on sale is the trap most people do not see coming. Depreciation taken under the actual-expense method after May 6, 1997 is not protected by the home-sale gain exclusion. It comes back as unrecaptured Section 1250 gain, taxed at up to 25%, when the home is sold. The rule reaches depreciation that was allowable even if never claimed, so skipping it does not avoid recapture where the taxpayer was entitled to take it. Some clients reasonably choose the simplified method for exactly this reason, since it produces nothing to recapture.

The gross income limitation quietly caps the direct deduction at the business's own profitability, and it cannot turn a profitable year into a loss. Anyone tracking a carryover from an actual-method year needs to remember that a simplified-method year forfeits it.

On the Florida side, claiming a home office at a modest business-use percentage does not put a homestead exemption at risk by itself. What does invite a county property appraiser's attention is a large business-use share of the home, or a separate structure run as a standalone business location. Keeping the business-use share modest and genuinely incidental to the residence is the safer posture.

A situation where this comes up

The client I picture most often here is an S corporation owner running a service business, a contractor, a consultant, a bookkeeper, who is at other people's locations for most of the actual work but does every bit of the billing, scheduling, and recordkeeping from a room at home. That owner often assumes they do not qualify, because they picture the principal-place test as requiring them to work from the room itself all day. That is not what the statute asks. If there is no other fixed location where the administrative side of the business happens, the room qualifies on that basis alone.

The version that needs correcting fast is the one where that same owner's corporation has already been paying them something labeled rent for the space. It usually started as a reasonable-sounding shortcut, pay the owner for the office the way a landlord would be paid, and nobody involved intended to create a problem. Fixing it means stopping the rent payments, adopting a written accountable plan, and reimbursing the same underlying costs through that plan instead.

What I look for before recommending either path is whether the space really is exclusive. An owner who wants the deduction but is not willing to stop using the room for anything else is not a documentation problem to solve. They do not have a qualifying space yet.