Home Office Deduction: The Rules That Actually Hold Up

The two tests

Exclusive and regular use

A space used only for business, on an ongoing basis. It needn't be a whole room, a defined area qualifies, but 'exclusive' is strict: the guest bedroom that's an office except when guests visit fails the test as written. The honest question: could you photograph the space and defend the word 'exclusively'? Field-service owners with a real dispatch desk, a wall of job files, and the printer that runs the business usually can. The dining table cannot.

Principal place of business

The test trades businesses worry about needlessly: your home office qualifies if it's where you perform administrative and management work, scheduling, invoicing, books, ordering, and you have no other fixed location where you do those things. A plumber who works in customers' homes all day and runs the business from the home office at night meets this test squarely; that's the exact scenario the rule was rewritten to cover. A separate shop or rented office where admin happens changes the answer.

The two methods

• Simplified: $5 per square foot, up to 300 sq ft, max $1,500, zero recordkeeping beyond the footage. The right answer for small spaces and simple lives
• Regular: business-use percentage (office sq ft ÷ home sq ft) applied to actual costs, rent or mortgage interest, utilities, insurance, repairs, plus depreciation for owners. More math, more records, and usually a meaningfully bigger number for anyone with a real office in an owned home

Worked comparison: a 200 sq ft office in a 2,000 sq ft home (10%) with $30,000 of annual home costs yields ~$3,000 under the regular method vs $1,000 simplified. The regular method's catch for homeowners: depreciation claimed is recaptured at sale (taxed then), worth modeling, rarely worth panicking over. Renters have no recapture and should almost always run the regular math.

The S corp wrinkle: accountable plan, not Schedule C

Once you're an S corporation, the Schedule C home office line disappears, the clean route is an accountable plan: the corporation reimburses you, the employee, for the business-use percentage of home costs, documented with an expense report. The reimbursement is deductible to the company and tax-free to you. Requirements: a written plan, actual expense substantiation, and timely reimbursement through payroll/AP, a fifteen-minute setup that S corp owners chronically skip, forfeiting the deduction entirely. (Entity context: How to Pay Yourself From an LLC (Without Creating IRS Trouble) ↗.)

What else the home office unlocks

Quietly, the bigger prize: with a qualifying home office as your principal place of business, driving from home to job sites becomes business mileage, not commuting. For a service business owner running crew visits, supply runs, and estimates, the mileage often outearns the office deduction itself. No qualifying office → first and last trips of the day are commuting, worth zero. This interaction is why the deduction deserves more respect than the folklore gives it.