OPEX, short for operating expenses, is the recurring cost of keeping a business running day to day: rent, payroll, utilities, insurance, office supplies, and similar items you use up within the year. For tax purposes, most operating expenses are fully deductible in the year you pay them, which is what separates them from capital expenditures that have to be depreciated over time.
What Counts as an Operating Expense
Federal tax law lets a business deduct “all the ordinary and necessary expenses paid or incurred during the taxable year in carrying on any trade or business.”1Office of the Law Revision Counsel. 26 U.S. Code 162 – Trade or Business Expenses Ordinary means common and accepted in your industry. Necessary means helpful and appropriate for your business, even if you could technically get by without it.2Internal Revenue Service. Ordinary and Necessary A restaurant buying cooking oil is ordinary. A software company buying cooking oil is harder to justify.
The defining feature is timing. Operating expenses get consumed within the current tax year. You pay for them, you use them up, and the benefit doesn’t stretch into future years. That’s what separates a monthly internet bill from a new delivery truck. Because operating expenses deliver their value immediately, you deduct the full amount in the year you pay, reducing your taxable income dollar for dollar.
The De Minimis Safe Harbor
Not every purchase fits neatly into one bucket. A $400 printer isn’t a major capital investment, but it will last several years. The IRS handles this gray zone through the de minimis safe harbor election. If your business doesn’t have audited financial statements filed with the SEC or a similar body, you can expense items costing up to $2,500 per invoice or per item rather than capitalizing them.3Internal Revenue Service. Notice 2015-82 – Increase in De Minimis Safe Harbor Limit for Taxpayers Businesses with certified or SEC-filed financial statements can use a $5,000 threshold. The cost must include everything on the same invoice, including delivery and installation.
Common Categories
Payroll is usually the single largest operating expense for any business with employees. This includes wages, salaries, benefits, and the employer’s share of payroll taxes. For sole proprietors, Schedule C breaks operating expenses into detailed line items covering contract labor, employee benefit contributions, and total wages paid.4Internal Revenue Service. Instructions for Schedule C (Form 1040) (2025)
Beyond payroll, the most common categories include:
- Rent and leases for office space, storefronts, warehouses, or leased equipment.
- Utilities: electricity, water, gas, internet, and phone service tied to business operations.
- Insurance premiums for general liability, property, workers’ compensation, and professional coverage.
- Office supplies and postage: paper, toner, shipping materials, and similar consumables.
- Repairs and maintenance that keep existing property in working condition without adding to its value or extending its life.
- Professional fees paid to accountants, attorneys, and consultants during the year.
- Vehicle expenses, either actual costs (fuel, insurance, repairs) or the IRS standard mileage rate, which is 72.5 cents per mile for 2026.5Internal Revenue Service. IRS Sets 2026 Business Standard Mileage Rate at 72.5 Cents Per Mile, Up 2.5 Cents
- Selling, general, and administrative costs (SG&A): marketing, advertising, administrative salaries, and corporate overhead that support the business but don’t directly produce goods.
Each of these gets consumed within the current year. That’s the unifying thread.
Home Office Expenses
Self-employed individuals who use part of their home regularly and exclusively for business can deduct a portion of housing costs. The IRS offers a simplified method: $5 per square foot of dedicated office space, up to 300 square feet, for a maximum deduction of $1,500.6Internal Revenue Service. Simplified Option for Home Office Deduction A regular method that calculates the actual percentage of rent, mortgage interest, utilities, and insurance attributable to the office space is also available and sometimes produces a larger deduction. Employees working remotely for a W-2 employer cannot claim this deduction under current federal law.
How OPEX Differs From CAPEX
The core distinction comes down to useful life. If you buy something that provides value beyond the current tax year, federal law generally requires you to capitalize the cost rather than deduct it all at once.7Office of the Law Revision Counsel. 26 U.S.C. 263 – Capital Expenditures A new roof on your warehouse, a fleet of delivery vans, a manufacturing machine — these are capital expenditures because they’ll serve the business for years.
The tax treatment splits sharply from there. Operating expenses reduce your taxable income in full the year you pay them. Capital expenditures get recovered gradually through depreciation, spread across a defined recovery period that matches the asset’s expected useful life. Under the Modified Accelerated Cost Recovery System (MACRS), office furniture and fixtures depreciate over 7 years, while a commercial building takes 39 years.8Office of the Law Revision Counsel. 26 U.S. Code 168 – Accelerated Cost Recovery System The IRS publishes detailed tables assigning virtually every type of business property to a specific recovery period.9Internal Revenue Service. Publication 946 – How to Depreciate Property
A practical way to think about it: if paying for it once keeps you covered for the year, it’s probably OPEX. If you’d still be using it three years from now, it’s likely CAPEX. The repair-versus-improvement question trips people up most often. Patching a leaky roof is a repair (OPEX). Replacing the entire roof with a longer-lasting material is an improvement (CAPEX).
Where OPEX Shows Up on the Income Statement
Operating expenses appear on the income statement right after gross profit, which is revenue minus the direct cost of producing goods or services. Subtract total OPEX from gross profit and you get operating income, also called EBIT (Earnings Before Interest and Taxes). This number reveals whether the core business is profitable on its own, before accounting for debt payments, investment income, or taxes.
A company with $2 million in revenue, $800,000 in cost of goods sold, and $900,000 in operating expenses has an operating income of $300,000. That figure is the clearest signal of how efficiently the business runs. A high ratio of operating expenses to revenue can flag waste, pricing problems, or a business model that costs too much to run. Investors and lenders focus on this section because it strips away noise. One-time gains, interest income, and tax strategies can all inflate or deflate net income at the bottom of the statement. Operating income reflects only what the business does every day.
What Happens if You Classify Wrong
Getting the OPEX-versus-CAPEX call wrong directly affects how much tax you owe and can trigger penalties. If you deduct a capital expenditure as an operating expense, you’ve overstated your deductions and underpaid your taxes. The IRS can impose an accuracy-related penalty equal to 20% of the underpaid tax attributable to negligence or disregard of tax rules.10Office of the Law Revision Counsel. 26 U.S. Code 6662 – Imposition of Accuracy-Related Penalty on Underpayments Interest accrues on top of that penalty until you pay the balance in full.11Internal Revenue Service. Accuracy-Related Penalty
The error runs the other way too. Capitalizing something that should be expensed means you’ve deducted too little, overpaid your taxes, and tied up cash unnecessarily. The IRS won’t penalize you for overpaying, but you’ve given the government an interest-free loan and weakened your cash position for no reason. Both mistakes are common near the repair-versus-improvement boundary and around the de minimis threshold.
Records You Need to Keep
Claiming operating expense deductions means being able to prove them if audited. The IRS requires records supporting every deduction for at least three years after filing the return. That retention period extends to six years if you fail to report income exceeding 25% of the gross income on your return, and to seven years if you claim a loss from worthless securities or bad debts.12Internal Revenue Service. How Long Should I Keep Records Employment tax records require at least four years. If you never file a return or file a fraudulent one, there’s no time limit at all.
In practice, holding onto receipts, invoices, bank statements, and mileage logs for at least seven years covers most scenarios. Digital copies are acceptable as long as they’re legible and accessible.