Small Business Tax Deductions: The Categories That Matter

The principle

The IRS lets businesses deduct "ordinary and necessary" expenses — ordinary meaning common in your trade, necessary meaning helpful and appropriate. Everything below is a specific application of that principle. The pattern to internalize: if it's genuinely for the business, documented, and not personal, it's usually deductible. The fights are always about documentation and personal-vs-business lines.

Home office

If you use part of your home regularly and exclusively for business, you have two methods:

• Simplified method: a flat IRS-set rate per square foot (up to 300 sq ft). Minimal paperwork.
• Regular method: deduct the business percentage of actual home expenses — mortgage interest or rent, utilities, insurance, repairs. More record-keeping, often a bigger deduction.

"Regularly and exclusively" is the tripwire: the space must be used for business on a regular basis and not for personal purposes. A guest room that doubles as an office fails the test.

Vehicle

Business driving is deductible; commuting from home to a regular workplace is not. Two methods:

• Standard mileage rate: the IRS publishes a per-mile rate each year. Multiply by business miles. Simple, and often generous.
• Actual expenses: gas, maintenance, insurance, depreciation, apportioned by business-use percentage.

Either way, you need a mileage log — the IRS is explicit about substantiation here. Apps that track automatically beat notebooks you fill in during April.

Retirement contributions

Often the largest deduction available to a profitable small business, and the most underused. The main vehicles:

• SEP IRA: simple to set up, contributions are deductible, limits scale with income.
• Solo 401(k): for owner-only businesses; allows both employer and employee contributions, usually the highest limits.
• SIMPLE IRA: a middle ground when you have a few employees.

Contribution deadlines and limits change yearly — confirm the current year's figures with IRS guidance or a professional. The strategic point stands regardless: retirement funding is one of the few deductions where the money stays yours.

Health insurance (self-employed)

Self-employed owners can generally deduct health insurance premiums for themselves, spouses, and dependents — a deduction with its own line on the return, separate from itemizing. S corporation owners above 2% ownership have specific rules here (premiums run through payroll). Details matter; the deduction is real either way.

Business meals

Business meals are generally 50% deductible when they have a clear business purpose — with a client, while traveling for business, or with employees for the employer's convenience (different rules apply). Document who, where, why, and how much. The days of the lavish fully-deductible client dinner are long gone; the 50% limit and documentation requirements are the current reality.

Startup costs and Section 179

• Startup costs: up to $5,000 deductible in year one (plus $5,000 of organizational costs), with phaseouts above $50,000 in total costs; the remainder amortized. Discuss classification with a professional.
• Section 179: lets you expense qualifying equipment purchases immediately instead of depreciating them over years. Limits and phaseouts are set annually — check the current year's figures.

What makes deductions survive scrutiny

• Business purpose, documented at the time. "Lunch with client X to discuss Q3 contract" beats a receipt alone.
• Separation. A dedicated business account turns "was this business?" from an argument into a statement.
• Consistency. Deductions claimed the same way every year look like a system. Novel ones in a high-income year look like a strategy.

When in doubt about a gray-area deduction, the cost of asking a professional is trivial compared to the cost of defending it.