IRS business deduction rules are governed primarily by Internal Revenue Code Section 162, which allows deductions for "ordinary and necessary" expenses paid or incurred in carrying on a trade or business. Key IRS publications for small business deductions include Publication 535 (Business Expenses), Publication 587 (Business Use of Your Home), and Publication 463 (Travel, Gift, and Car Expenses). Tax Sherpa helps business owners stay compliant with IRS rules while maximizing every available deduction.
Key Takeaways
- IRC Section 162 is the foundation — expenses must be "ordinary and necessary" for your trade or business
- Publication 535 (Business Expenses) is the IRS's comprehensive guide to business deductions
- The IRS looks for documentation and business purpose — not just whether you spent the money
- Common audit triggers: disproportionate deductions relative to income, consistent losses, large meal/travel/vehicle claims
- Safe harbor provisions exist for home office, vehicle, and other areas — use them to minimize risk
Key IRS Publications for Business Deductions
Publication | Topic | What It Covers |
Pub 535 | Business Expenses | Master guide to all business deductions |
Pub 587 | Business Use of Home | Home office deduction rules and calculations |
Pub 463 | Travel, Gift, and Car Expenses | Travel, meal, gift, and vehicle deduction rules |
Pub 946 | How to Depreciate Property | Depreciation methods, Section 179, bonus depreciation |
Pub 560 | Retirement Plans for Small Business | SEP IRA, SIMPLE IRA, qualified plans |
Pub 334 | Tax Guide for Small Business | Overview for sole proprietors |
Pub 583 | Starting a Business | Tax responsibilities, record-keeping |
Pub 925 | Passive Activity and At-Risk Rules | Limitations on loss deductions |
Common Audit Triggers for Business Deductions
- Consistent losses — Reporting business losses for 3+ years may trigger hobby loss examination
- Large vehicle deductions — Especially 100% business use claims on personal vehicles
- Excessive meal and entertainment — Meal deductions that seem disproportionate to business size
- Home office deduction — While legitimate, large home office deductions relative to income draw attention
- Round numbers — Reporting perfectly round expense amounts (e.g., exactly $5,000) suggests estimation rather than actual tracking
- Cash-heavy businesses — Industries with significant cash transactions face increased scrutiny
- Unreported income — When the IRS has information returns (1099s) that don't match your reported income
IRS Safe Harbors to Know
Safe Harbor | What It Provides |
Home office simplified method | $5/sq ft, max 300 sq ft — no audit risk for calculation method |
De minimis safe harbor | Deduct items under $2,500 (or $5,000 with audited financial statements) instead of capitalizing |
Standard mileage rate | IRS-established rate eliminates need to prove actual vehicle costs |
3-of-5 year profit test | Presumption of business (not hobby) if profitable in 3 of 5 years |
Record-Keeping Best Practices
The IRS recommends keeping business records for at least 3 years from the filing date (the standard statute of limitations for audits). However:
- 6 years if the IRS suspects underreporting of income by more than 25%
- 7 years if you claim a loss from worthless securities or bad debt deduction
- Indefinitely if you don't file a return or file a fraudulent return
Best practice: Keep all business records for 7 years to cover all scenarios.
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