Updated October 24, 2026. Quick answer: Tax Topic 509 is the IRS page on business use of home. It says self-employed people and partners may deduct certain expenses for the part of the home used for business, if that space meets one of the listed uses. Two methods are available: the regular method and a simplified option.
Quick reference
| Item | What the IRS topic says |
|---|---|
| Who may deduct | “Whether you’re self-employed or a partner, you may be able to deduct certain expenses for the part of your home that you use for business.” |
| Mixed personal use | “you can’t deduct business expenses for any part of your home that you use both for personal and business purposes.” |
| Regular method form | “Self-employed taxpayers filing Schedule C (Form 1040), Profit or Loss From Business (Sole Proprietorship) first compute this deduction on Form 8829, Expenses for Business Use of Your Home.” |
| Simplified option rate | “allows qualifying taxpayers to use a prescribed rate of $5 per square foot of the portion of the home used for business (up to a maximum of 300 square feet) to compute the business use of home deduction.” |
| Income limit | “you may not deduct business expenses in excess of the gross income limitation.” |
What the space must be used for
The topic lists the qualifying uses. It says “To deduct expenses for business use of the home, you must use part of your home as one of the following:” The first item is “Exclusively on a regular basis as your principal place of business for your trade or business;” and the list ends with “As a daycare facility.”
The mixed use rule is blunt. The topic says “you can’t deduct business expenses for any part of your home that you use both for personal and business purposes.” Its example is an attorney who writes briefs in a den that is also used personally. For the home office basics, see our home office page.
Which expenses count and the regular method
The topic says “Deductible expenses for business use of your home include the business portion of real estate taxes, mortgage interest, rent, casualty losses, utilities, insurance, depreciation, maintenance, and repairs.”
On the regular method, it says “You compute the business use of home deduction by dividing expenses of operating the home between personal and business use.” The form is named too: “Self-employed taxpayers filing Schedule C (Form 1040), Profit or Loss From Business (Sole Proprietorship) first compute this deduction on Form 8829, Expenses for Business Use of Your Home.” Our Form 8829 page and the Schedule C line 30 page cover the lines.
The simplified option and the income limit
The topic describes the alternative. It says “allows qualifying taxpayers to use a prescribed rate of $5 per square foot of the portion of the home used for business (up to a maximum of 300 square feet) to compute the business use of home deduction.” It adds “Under this safe harbor method, depreciation is treated as zero and the taxpayer claims the deduction directly on Schedule C (Form 1040).”
Both methods share a cap: “you may not deduct business expenses in excess of the gross income limitation.” On carryovers, the topic says “There’s no carryover provision under the safe harbor method, but you may elect into and out of the safe harbor method in any given year.” It points to Publication 587 for the detail.
Where this comes from
This page describes the IRS page titled Topic no. 509, Business use of home, as served on irs.gov on October 24, 2026. The IRS page shows that it was last reviewed or updated on 24 Sep 2026. The IRS can change a topic after we read it, and the IRS page controls. General information, not tax or legal advice.
Common mistakes
- Deducting a room that is also used personally. The topic says you “can’t deduct business expenses for any part of your home that you use both for personal and business purposes”
- Deducting upkeep on rooms not used for business. The topic names examples such as “lawn care or painting a room not used for business”
- Expecting a carryover under the simplified option. The topic says “There’s no carryover provision under the safe harbor method”
- Ignoring the income cap. The topic says “you may not deduct business expenses in excess of the gross income limitation”
Related: IRS tax topics by number, Home office deduction, Form 8829, Schedule C (Form 1040), Schedule C line 30: business use of your home, and Form 8829 lines 1 to 7.
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Answer againSources
- IRS, Topic no. 509, Business use of home (irs.gov): https://www.irs.gov/taxtopics/tc509
- IRS, Tax topics index (irs.gov): https://www.irs.gov/taxtopics
Read from the IRS pages linked above on October 24, 2026. General information, not tax or legal advice. The IRS topic page and the instructions for your own form control, and your own facts decide the outcome.