Ordinary and Necessary: The Two-Word Test Behind Every Business Tax Deduction

Here is something that surprises most small business owners: the IRS publication that defined deductible business expenses for decades no longer exists. If you visit the old Publication 535 page today, you land on a "Guide to business expense resources" instead — the IRS discontinued Publication 535 after the 2022 revision and scattered its chapters across a dozen other publications.

But the two-word test at the heart of that publication is alive and well, because it comes from the tax code itself, not from the booklet. Section 162(a) allows a deduction for "all the ordinary and necessary expenses paid or incurred during the taxable year in carrying on any trade or business." Every dollar you deduct — rent, software, mileage, insurance — has to clear those two words. Here is what they actually mean, where the old rules live now, and how to keep your deductions defensible.

"Ordinary" Means Normal for Your Industry, Not Business in General​

An ordinary expense is one that is common and accepted in your trade or business. The key phrase is your trade or business. The test is industry-specific, which cuts both ways.

A freelance photographer deducting a $3,000 lens rental for a wedding shoot? Ordinary — clients expect professional gear. A bookkeeping firm deducting courtside season tickets as "client development"? Almost certainly not ordinary for bookkeepers, even if season tickets might be unremarkable for a sports marketing agency. The IRS and the courts ask what businesses like yours normally spend money on, not what business owners in general spend money on.

This is why niche-industry expenses that look strange from the outside usually survive scrutiny: specialty tools, trade-association dues, industry certifications, protective equipment. If your competitors all pay for it, you can explain it in one sentence to an auditor. If no one in your field has ever paid for it, you need a much better story — which is your first warning sign that the expense may fail the test.

"Necessary" Means Helpful, Not Indispensable​

A necessary expense is one that is helpful and appropriate for your trade or business. It does not have to be indispensable. You do not have to prove your business would collapse without it — only that a reasonable business owner in your position could see the point.

That project-management subscription, the coworking membership that gets you out of a noisy apartment, the professional-development course that keeps your skills current: none of them is strictly required to keep the lights on, and all of them can be necessary. The IRS does not get to second-guess your business judgment and substitute a cheaper alternative. If the expense genuinely serves the business, "you could have done it for less" is not a valid objection.

There is one important qualifier. While the code says nothing about an expense being "too large," compensation and some other categories carry a reasonableness limit — Section 162(a)(1) allows only "a reasonable allowance for salaries or other compensation for personal services actually rendered." Paying your teenager a $60,000 salary for occasional filing work will attract exactly the attention you would expect. Necessary gives you latitude; it does not give you a blank check.

Where Publication 535's Rules Live Now​

Since the IRS retired Publication 535, its material is mapped to other resources. The old chapters did not change substance — they moved house. Here is where to look now for the topics owners ask about most:

Two moves deserve special attention. First, the self-employed health insurance worksheet that used to sit in Publication 535 is now its own form — Form 7206 — so if you deduct health premiums for yourself, that is where the calculation lives. Second, Publication 334 has effectively become the default starting point for sole proprietors; bookmark it the way you used to bookmark Publication 535.

What Passes the Test in Practice​

Most of what a small business spends falls into a handful of categories that clearly satisfy both halves of the test:

• Salaries, wages, and contractor payments — deductible when reasonable and for services actually rendered, including the employer share of payroll taxes.
• Rent and lease payments — for office, retail, studio, or equipment you use but do not own.
• Supplies, software, and subscriptions — from paper clips to the accounting platform and cloud hosting that run the operation.
• Professional services — legal, tax preparation, bookkeeping, and consulting fees tied to the business.
• Insurance premiums — liability, property, business interruption, workers' compensation, and health coverage within the applicable rules.
• Advertising and marketing — website costs, online ads, signage, and sponsorships that promote the business.
• Business taxes and licenses — sales tax you collect and remit aside, deductible taxes include the employer share of Social Security and Medicare, state unemployment tax, and business license fees.
• Interest on business debt — subject to the Section 163(j) business-interest limitation for larger businesses.

Notice what these have in common: each is common in its industry, helpful to the operation, and incurred while carrying on the business. That last clause matters more than people think. Pre-opening spending and hobby-like activities get different treatment, which brings us to the traps.

The Limits That Shrink Otherwise-Good Deductions​

Passing the ordinary-and-necessary test is necessary but not always sufficient. Several categories clear the test yet face their own caps and carve-outs:

• Business meals are generally 50% deductible. The temporary 100% deduction for restaurant meals expired after 2022. The meal still has to be ordinary and necessary — and not lavish or extravagant — and then you deduct half.
• Entertainment is effectively gone. Since the Tax Cuts and Jobs Act, outlays for entertainment, amusement, or recreation — sporting events, theater tickets, golf outings — are nondeductible even when clients are present. Do not relabel them as meals or marketing.
• Business gifts are capped at $25 per recipient per year. That ceiling has not moved in decades and it will not cover much more than a token. Amounts above it are simply nondeductible.
• Commuting and everyday clothing are personal. Driving from home to your regular workplace is commuting, not business travel, and clothing suitable for everyday wear is nondeductible even if you only wear it to work. Deductible uniforms and protective gear are the exception because they are not suitable for ordinary wear.
• Fines, penalties, and political contributions are out. Government fines, parking tickets on a business vehicle, and contributions to political campaigns or lobbying all fail regardless of business motive.

Startup spending gets its own special rule worth knowing before you launch: you can generally deduct up to $5,000 of startup costs in your first year (reduced dollar-for-dollar once startup spending exceeds $50,000), with the remainder amortized over 15 years. That election exists precisely because pre-opening costs are incurred before you are "carrying on" the business.

Deduct Now or Capitalize? The Timing Question​

Even when an expense is clearly business-related, you cannot always deduct the whole thing this year. Supplies and costs consumed within the year are current deductions. Longer-lived investments — equipment, vehicles, buildings, and improvements that extend an asset's life or increase its value — generally have to be capitalized and recovered through depreciation over time.

The gray zone is repairs versus improvements. Patching a leaking roof on your rental studio is a repair; replacing the entire roof system is an improvement. Repainting the office is maintenance; gutting and reconfiguring it is a betterment. The distinction follows the economics: spending that keeps property in ordinarily efficient operating condition is deductible now, while spending that makes it better, bigger, or longer-lived gets capitalized.

Getting this wrong in the aggressive direction — expensing a $40,000 buildout — is one of the most common adjustments in small-business audits. When a project starts to look like an improvement, slow down, depreciate it properly on Form 4562, and consider whether Section 179 expensing gets you much of the same benefit legitimately.

The Substantiation Trap: Records Beat Eligibility​

Ask tax preparers why deductions die in audits and most give the same answer: poor records, not ineligible expenses. An expense can be perfectly ordinary and necessary and still be disallowed because you cannot prove it. The burden of proof is on you.

Congress sets a higher bar for the categories most prone to abuse. Under Section 274, travel, meal, vehicle, and gift expenses require heightened substantiation: for each item you need the amount, the time and place, the business purpose, and the business relationship of the people involved. Credit-card statements alone do not cut it — they show amount and place but say nothing about purpose. A mileage log reconstructed months later from memory invites skepticism; a log kept as you drive does not. Courts apply only a narrow exception for good-faith estimates (the so-called Cohan rule), and it does not cover the Section 274 categories at all — for travel, meals, and vehicles, inadequate records mean no deduction, full stop.

The fix is mostly habit, not effort. Capture the receipt at the point of spend, jot the business purpose while it is fresh — "lunch with supplier re: Q1 pricing" takes ten seconds — and keep a running mileage log instead of rebuilding one in April. Digital copies are fine; the IRS accepts electronic records as long as they are legible and complete. Separate business spending onto dedicated accounts so personal transactions never mingle with deductible ones, and label any accidental personal charge immediately rather than burying it.

Build a Recordkeeping Habit That Survives an Audit​

The ordinary-and-necessary test rewards businesses whose books tell a clear story. When every expense sits in a labeled account with a receipt and a stated business purpose, "common and accepted in your industry" and "helpful and appropriate" practically demonstrate themselves. When expenses live as unlabeled card charges in a mixed personal account, even legitimate deductions become hard to defend.

A workable system has four parts: dedicated business accounts so commingling never starts, point-of-spend capture so purpose notes are contemporaneous, a monthly review where you categorize everything while memory is fresh, and a filing setup — digital is fine — where receipts live for at least as long as the IRS can ask for them. None of this requires enterprise software. It requires consistency, which is exactly what plain-text, version-controlled books make easy to maintain.

Keep Every Deduction You Deserve​

Understanding the ordinary-and-necessary standard puts you ahead of most filers, but the standard only protects deductions your records can prove. Beancount.io gives you plain-text accounting with complete transparency and control over your financial data — every expense categorized, timestamped, and backed by your own version history. Get started for free and build the paper trail your deductions deserve.