Home Office Deduction: What Counts, What Doesn't, and How to Calculate It

The home office deduction trips people up in two directions. Half are afraid to take it at all, convinced it's an audit trigger. The other half claim it carelessly and either get it wrong or create real problems down the road.

Here's what the IRS actually requires, what you can deduct, and how the two calculation methods compare.

Who Qualifies

The home office deduction is available to self-employed people who use part of their home exclusively and regularly for business. Both words matter.

Exclusively means the space is used for business and nothing else. A dedicated office qualifies. A kitchen table where you also eat dinner doesn't. A spare bedroom where you work and guests sleep doesn't. The IRS takes "exclusively" literally — there's no de minimis carveout for the corner of a room you sometimes use personally.

Regularly means routine use, not occasional. Using a space for a few hours once a month likely doesn't qualify. Using it every workday does.

Two other qualifying tests: the space must be your principal place of business (or a place where you meet clients or customers regularly), and if it's a separate structure, it must be used for business. For most self-employed people, the "principal place of business" test is the relevant one.

One important exception: W-2 employees cannot take this deduction, even if they work from home. The 2017 tax law eliminated that option for employees. This deduction is for the self-employed only.

What You Can Deduct

If you qualify, two categories of expenses are deductible through the home office:

Direct expenses are costs that apply only to the office space itself. Painting the office, fixing a window in that room, furniture purchased specifically for the office. These are 100% deductible.

Indirect expenses apply to the home as a whole — mortgage interest, rent, utilities, homeowner's insurance, general repairs, depreciation. These are deductible in proportion to the size of the office relative to the home.

The proportion calculation: divide the square footage of the dedicated office space by the total square footage of the home. A 200 sq ft office in a 2,000 sq ft house = 10% of indirect expenses are deductible.

The Two Calculation Methods

You have a choice: the simplified method or the regular (actual expense) method. They work differently and produce different results.

Simplified Method

Rate: $5 per square foot of office space. Maximum: 300 square feet, so the max deduction is $1,500/year.

Fast. No depreciation. No need to track actual home expenses. The tradeoff is a lower deduction for most people with meaningful home costs.

The simplified method also doesn't require recapture when you sell the home. More on that below.

Regular (Actual Expense) Method

Calculate your office percentage, then apply it to your actual home expenses. Mortgage interest, rent, utilities, insurance, repairs, depreciation — all subject to the percentage.

More paperwork. Requires tracking actual costs through the year. Usually produces a larger deduction, especially if you have a high mortgage, significant utility costs, or live in an expensive area.

The depreciation piece requires using Form 8829 and calculating the depreciable basis of the home. When you eventually sell the home, depreciation taken through the home office deduction is subject to recapture — meaning some of that benefit comes back as taxable income at sale. This is a real consideration if you've owned the home for years and taken significant depreciation.

Which One Wins

Simplified is better if: your office is small (under ~150 sq ft), your actual home expenses are low, or you want zero complexity and don't care about the depreciation question.

Regular is better if: your office is large, your home expenses are high (mortgage + utilities in a pricey area), and you're comfortable with the depreciation recapture consideration.

Run both calculations. The regular method often wins by $500–$2,000 annually for people with real home costs, which compounds significantly over several years.

The Deduction Limitation Rule

The home office deduction can't create a net loss from your business. Your deduction is limited to your net income from the business. If your business made $3,000 this year, you can't deduct $5,000 in home office expenses and show a loss.

Unused deduction under the regular method carries forward to future years. Unused simplified method deductions don't — they disappear.

This matters for part-year businesses, seasonal work, or anyone with a slow first year. If you're below the limit, the simplified method's cleanliness becomes more attractive since you lose the benefit either way.

Renter vs. Homeowner

Renters have a simpler situation. Deductible expenses include rent (proportional to office %), utilities (proportional), and renter's insurance (proportional). No depreciation, no recapture on sale.

Homeowners have more to track and more to gain. Deductible expenses include mortgage interest (proportional), property taxes (proportional — though note you also deduct these on Schedule A as an itemized deduction, so the coordination matters), utilities, insurance, and depreciation on the home itself.

If you rent, the simplified method is often competitive with regular because depreciation isn't a factor. If you own, the regular method typically wins by a larger margin.

Common Mistakes

The "sometimes I work there" mistake. Working from a room occasionally doesn't create a home office deduction. The space has to be dedicated to business use.

The "my whole spare room" mistake. If you store personal stuff in the office, the exclusive use test fails. Clear it out or acknowledge the space doesn't qualify.

Forgetting to track throughout the year. Trying to reconstruct utility bills and insurance costs in April is painful. Set a folder or a note file and log costs monthly.

Using the simplified method without checking the math. $1,500/year sounds fine until you realize your actual deduction would have been $3,200. Run both numbers before filing.

Depreciation recapture surprise. If you've taken significant depreciation over years of home office deductions and then sell the house, recapture at 25% hits that amount. Not a reason to avoid depreciation — just a reason to know it's coming.

The Audit Question

The home office deduction's reputation as an audit trigger is mostly folklore from the 1980s and 1990s when the rules were murkier and enforcement was different. The deduction is legitimate, common, and documented on Form 8829 (or via the simplified method directly on Schedule C).

That said: the deduction is only worth taking if you actually meet the requirements. Don't stretch the exclusive use rule. Don't estimate your square footage generously. Take what you're entitled to, document it, and don't take what you're not.