Home Office and Mileage Deductions: What's Allowed, and Will It Trigger an Audit?

Educational guide — the two most misunderstood (and most feared) small business deductions

Of all the deductions available to self-employed people and small business owners, home office and mileage carry an outsized reputation for triggering an IRS audit. That reputation isn't entirely fair — but it isn't entirely wrong, either. Here's what's actually true.

Does Claiming a Home Office Deduction Trigger an Audit?

Not automatically — but it's a historically abused deduction, and the IRS knows it. Every return gets a statistical score (the IRS's Discriminant Function, or DIF score) comparing it against typical returns at similar income levels and in similar industries. Home office claims that look disproportionate, inconsistent with the type of work reported, or paired with other red flags (a Schedule C loss, unusually high expenses relative to revenue) are more likely to push a return's score high enough for manual review. A clean, well-documented, reasonably sized home office claim on an otherwise normal return is unlikely to be the thing that gets you audited on its own.

The overall individual audit rate is low — under 0.5% in recent years — but it rises meaningfully for self-employed filers, cash-intensive businesses, and higher-income taxpayers. Home office deductions are more common among exactly those groups, which is part of why the deduction has its reputation.

Who Can Actually Claim a Home Office Deduction

This is the detail that trips up the most people: W-2 employees cannot claim a home office deduction at all — even if their employer requires them to work from home. This has been the rule since 2018 (the Tax Cuts and Jobs Act suspended the miscellaneous itemized deduction that used to allow it), and recent legislation has made that suspension permanent. It doesn't matter how legitimate or necessary the home office is for a W-2 employee's job — the deduction simply isn't available to them under current law.

The deduction is available to:

• Sole proprietors and single-member LLC owners — claimed directly on Schedule C (Form 8829)
• Partners in a partnership, generally through Unreimbursed Partnership Expenses (UPE) on Schedule E, if the partnership agreement requires them to bear the cost personally
• S-corp or C-corp owner-employees — but only through a properly documented Accountable Plan, since they're technically employees of their own corporation

The Two Tests That Actually Matter

To qualify at all, the space must pass both of these:

1. Exclusive use — the space is used only for business, not also as a guest bedroom, playroom, or general living space. A desk in the corner of a room you also use for other things generally doesn't qualify for the space it occupies unless it's a clearly defined, separate area.
2. Regular use — you use the space consistently for business, not occasionally.

There's also a broader requirement that the space be your principal place of business, or a place you regularly meet clients/customers, or a separate structure used for business.

Two Ways to Calculate It

• Simplified method — $5 per square foot of qualifying space, up to 300 square feet (a maximum $1,500 deduction). No need to track actual expenses; less paperwork, less audit exposure, but often a smaller deduction.
• Regular method — calculate the actual business-use percentage of your home (square footage of office ÷ total home square footage) and apply that percentage to your actual home expenses (utilities, insurance, mortgage interest or rent, repairs, depreciation). Usually a larger deduction for people with significant home expenses, but requires real documentation.

What Documentation Actually Protects You

If you're ever asked to substantiate a home office deduction, this is what actually holds up:

• A simple floor plan or sketch showing the dedicated space and its square footage
• Photos of the space, ideally showing it's clearly set up for business use only
• A record of the exclusive/regular use — even a basic calendar or log of work performed there
• Copies of the utility bills, mortgage or rent statements, and insurance used to calculate the deduction (if using the regular method)

The single most common way people lose this deduction on audit isn't that the space wasn't used for business — it's that the space also had a clear personal use (a bed, a TV, kids' toys), which fails the "exclusive use" test regardless of how much legitimate work happens there.

Mileage: A Different Kind of Documentation Problem

Vehicle expense deductions face a similar reputation, for a similar reason: mileage logs are easy to estimate loosely and hard to verify after the fact, and the IRS knows this.

Two ways to calculate vehicle deductions:

• Standard mileage rate — a per-mile rate set annually by the IRS, multiplied by your documented business miles. Simpler, but you must still track actual mileage.
• Actual expense method — track the real cost of operating the vehicle (gas, insurance, repairs, depreciation) and apply your business-use percentage.

What real documentation looks like: a contemporaneous mileage log — recorded at or near the time of the trip, not reconstructed from memory months later — showing the date, starting and ending odometer readings (or total miles), destination, and business purpose of each trip. A mileage-tracking app that logs GPS-based trips in real time is generally far more defensible than a notebook filled in once a year before filing.

A common and costly mistake: claiming 100% business use of a vehicle that's also clearly used for personal errands, commuting, or family use. Commuting from home to a regular workplace is never deductible, even for self-employed people — only business travel beyond normal commuting counts.

The Bigger Picture: Don't Skip Legitimate Deductions Out of Fear

The single biggest mistake isn't claiming these deductions — it's either overclaiming them without documentation, or avoiding them entirely out of audit anxiety and leaving legitimate tax savings on the table. A well-documented, reasonably calculated home office or mileage deduction is a normal, expected part of a small business or self-employed tax return. The IRS's own guidance (Publication 587 for home office, Publication 463 for vehicle and travel expenses) lays out exactly what's required — the deduction exists precisely for taxpayers who meet those requirements.

This article is for general educational purposes only and does not constitute tax, legal, or financial advice. Requirements for home office and vehicle deductions are fact-specific, and documentation standards matter significantly if a return is examined. Consult a qualified tax professional or CPA, and see IRS Publication 587 (Business Use of Your Home) and Publication 463 (Travel, Gift, and Car Expenses), for guidance specific to your situation.

Tax Code References

• IRC §280A — Governs the business use of a home, including the "exclusive use" and "regular use" tests and the "principal place of business" requirement that a home office deduction must satisfy.
• IRC §67(g) — Suspension of miscellaneous itemized deductions (including unreimbursed employee business expenses, which historically covered home office claims by W-2 employees); enacted by the Tax Cuts and Jobs Act (TCJA) of 2017 through 2025, made permanent by the One Big Beautiful Bill Act (OBBBA), Pub. L. 119-21 (signed July 4, 2025) — the reason W-2 employees cannot claim this deduction at all under current law.
• Revenue Procedure 2013-13 — Established the simplified method for the home office deduction ($5 per square foot, up to 300 square feet).
• IRS Publication 587, Business Use of Your Home — Detailed IRS guidance on qualifying for and calculating the home office deduction under both the regular and simplified methods.
• IRC §162 — General rule allowing deduction of ordinary and necessary trade or business expenses, the underlying authority for both home office and vehicle expense deductions.
• IRC §274(d) — Strict substantiation requirements for travel, and "listed property" including vehicles — the basis for the IRS's documentation expectations (contemporaneous mileage logs, business purpose, etc.).
• IRS Publication 463, Travel, Gift, and Car Expenses — Detailed IRS guidance on the standard mileage rate method versus actual expense method, recordkeeping requirements, and the non-deductibility of ordinary commuting.
• Annual IRS standard mileage rate notices (e.g., Notice 2025-5 and its annual successors) — Set the per-mile rate for the standard mileage method each year; the rate changes annually and should be verified for the current tax year.
• Revenue Ruling 70-16 and Schedule E instructions — Governs Unreimbursed Partnership Expenses (UPE), including home office and mileage costs a partner is required to bear personally under a partnership agreement.
• IRC §62(c) and Treas. Reg. §1.62-2 — Accountable plan rules, the mechanism by which S-corp and C-corp owner-employees can still be reimbursed tax-free for home office and mileage costs despite the §67(g) suspension.

Tax law changes frequently, including through annual inflation adjustments (such as the standard mileage rate) and new legislation. Figures and rules above reflect the law as of this writing (2026) and should be verified against current IRS guidance before relying on them.