Business Expense and Home Office Deductions: Records That Hold Up

Two statutes do most of the work. Section 162 allows a deduction for expenses that are ordinary and necessary in carrying on a trade or business. Section 280A generally disallows deductions connected to a dwelling and then carves out an exception for a space used exclusively and regularly for business. Neither turns on whether the spending felt justified. Both turn on whether a specific, contemporaneous record connects the money to the business — which is why deductions are usually lost on the file rather than on the law.

1.What section 162 actually requires

Four elements sit behind every business deduction. The expense must be paid or incurred in carrying on a trade or business, which excludes start-up costs before the business began and hobbies that never became one. It must be ordinary, meaning common and accepted in that line of work — not necessarily frequent, but not eccentric. It must be necessary, meaning helpful and appropriate, a low bar courts rarely use to deny. And it must be reasonable in amount, which is where extravagance is policed.

Certain expenses are disallowed by other provisions regardless of how ordinary they are: fines and penalties paid to a government, illegal payments, most lobbying costs, and personal, living, and family expenses. Mixed-purpose spending is allocated, and the burden of showing the business share falls on the taxpayer.

2.The records that hold up

For most expenses, the general rule is that the taxpayer must keep records sufficient to establish the amount, and courts have long allowed a reasonable estimate where some deduction is clearly allowable but the exact figure is unproven. That leniency has a large exception. Travel, certain entertainment-related items, business gifts, and listed property carry strict statutory substantiation: without records or corroborating evidence establishing amount, time, place, and business purpose, no deduction is allowed at all, however credible the testimony.

• Amount, date, place, and business purpose recorded at or near the time of the expense.
• For meals and travel, the business relationship of the people present.
• For vehicles, total miles for the year and business miles separately, with the beginning and ending odometer readings.
• Receipts for expenses above the level at which the regulations require documentary evidence, and for lodging regardless of amount.
• A separate business bank account and card, so the classification exercise starts from clean data rather than from a personal statement.

Caution: Bank and card statements alone rarely suffice for the strict-substantiation categories. A statement proves an amount was paid to a restaurant. It does not prove who was there or what business was discussed.

3.The section 280A test

The home office exception has two conditions that must both be met, and then a third that identifies the kind of use qualifying.

The space must be used exclusively for business. This is read strictly: a desk in a spare bedroom that also holds guests fails, and a dining table used for work fails. The space need not be a whole room, but the portion claimed must have no personal use at all. Two narrow exceptions exist in the statute, for storage of inventory or product samples in a home that is the sole fixed location of the business, and for licensed daycare facilities.

The space must also be used regularly, not occasionally. Sporadic or incidental business use fails even if it is exclusive.

Then the use must fall into one of the qualifying categories: the principal place of business; a place used to meet patients, clients, or customers in the normal course of business; or a separate structure not attached to the dwelling used in connection with the business. The first category was widened by Congress after a restrictive Supreme Court decision, so that a home office qualifies as the principal place of business where it is used for administrative or management activities and there is no other fixed location where those activities are substantially conducted. That is the provision that makes the deduction available to a contractor who works on customer sites but does all scheduling and billing at home.

A separate limitation caps the deduction at the gross income from the business use, reduced by other allocable deductions. Amounts disallowed by that cap generally carry forward. And employees stand differently from the self-employed: since 2018 unreimbursed employee business expenses have been unavailable as a deduction under a statutory suspension of miscellaneous itemized deductions, a provision Congress has revisited more than once. As of mid-2026 an employee working from home should confirm the current position before assuming any deduction exists, and should look first to an accountable reimbursement plan through the employer, which is not income to the employee at all.

Simplified method or actual expenses

Actual expense method

Allocate the business percentage of mortgage interest or rent, property tax, insurance, utilities, repairs, and depreciation. Produces a larger deduction in most cases, requires the most records, and creates depreciation that is recaptured when the home is sold.

Simplified method

Multiply the qualifying square footage by a rate the IRS prescribes, up to a capped area. No depreciation is claimed and none is recaptured. Far less recordkeeping, and the choice can be made year by year.

The rate and the area cap are published by the agency and can change, so both should be read from the Small Business and Self-Employed Tax Center at the time of filing. Note that the exclusive and regular use tests apply identically under both methods; the simplified method simplifies the arithmetic, not the qualification.

4.Where the states diverge

State income tax systems generally begin from a federal number, which means a federal business deduction usually flows through to the state return automatically. The divergences are real, though, and they cluster in predictable places. Some states decouple from federal depreciation and bonus depreciation rules, requiring their own schedules. Some did not follow the federal suspension of employee business expense deductions, so an employee denied a home office deduction federally may still claim one on a state return — California and New York have both taken positions distinct from the federal one at various points.

Separately, state and local taxes a business pays are themselves deductible business expenses, including the sales and use taxes discussed in sales and use tax nexus after Wayfair. And a home office in one state used to serve customers in another can raise state income tax nexus questions for the business that have nothing to do with the deduction.

5.Questions this raises

Does claiming a home office increase my chance of being audited?

The belief is widespread and largely unsupported. Returns are selected mainly by statistical scoring and by information-return matching, and a home office claim consistent with the rest of the return is unremarkable. What draws attention is a deduction out of proportion to reported business income, or one claimed alongside a business showing losses year after year. Claim what qualifies and document it.

What happens to the home office deduction when I sell the house?

Depreciation claimed on the business portion is generally recaptured on sale and taxed, even where the gain otherwise falls within the exclusion for a principal residence. This is the main structural cost of the actual expense method, and it is why the simplified method appeals to owners planning to sell. Recapture applies to depreciation allowed or allowable, so skipping the deduction while qualifying does not avoid it.

My business ran at a loss for several years. Is it still a business?

It can be, but sustained losses invite the argument that the activity is not engaged in for profit, which sharply limits deductions. The analysis weighs factors including how businesslike the operation is, the taxpayer's expertise, time devoted, expectation that assets will appreciate, and the personal pleasure derived. Separate books, a written plan, and documented changes of method in response to losses all help considerably.

Can I deduct the cost of getting the business started?

Not as ordinary business expenses, because section 162 requires that the business already be carried on. Start-up and organizational costs are treated under separate provisions that allow a limited immediate deduction with the remainder amortized over a period of years. The distinction between investigating a business and operating one turns on when the enterprise actually opened for business, so the date should be documented.

6.Setting the system up once

1. Separate the money. A dedicated business account and card removes most classification disputes before they arise.
2. Capture at the point of spending. Photograph receipts immediately and note the purpose and attendees while you remember them.
3. Keep the mileage log in the vehicle or in an application that records trips automatically. Reconstruction is the most common cause of a lost vehicle deduction.
4. Photograph the home office once a year and keep a floor plan with measurements. This is the evidence examiners ask for, and it is trivial to produce in advance and impossible to fake later.
5. Reconcile monthly, not annually. A misclassified transaction is easy to fix in the same month and nearly impossible to explain a year later.
6. Retain records for the full assessment period, and longer for anything supporting depreciation basis, which is needed when the asset is sold.

Good files also make everything downstream easier: the estimated payment computations in estimated tax payments and the underpayment penalty, the substantiation logic in substantiating charitable contributions, and any correction later made through amending a return. The agency's own guidance on what to keep and for how long sits alongside its examination material.