A note on sources: IRS Publication 535 (Business Expenses) was officially discontinued after tax year 2022. The guidance it contained now lives across IRS Publication 334 (Tax Guide for Small Business) and other topic-specific IRS publications. Many articles on this topic still cite Publication 535 as if it's current — this one doesn't. All references below reflect current IRS guidance and the Internal Revenue Code as of 2025.

Every business expense deduction you claim starts with the same two-word test straight out of the tax code: ordinary and necessary. Those words come directly from IRC § 162(a) — the Internal Revenue Code section that governs business deductions — and they've been the foundation of business expense law for decades. Get this test right and you understand the logic behind virtually every deduction your business can take. Get it wrong and you're exposed to disallowed deductions, accuracy-related penalties, and in serious cases, an audit.

But there's a dimension to business expense deductions that most guides miss entirely: how those deductions affect your tax return — and how that tax return is used when you apply for a business loan. Every dollar you legitimately deduct reduces your taxable income. For the IRS, that's the point. For a lender evaluating your loan application, it's a number they have to work around. Understanding both sides of that equation is what this article is about.

The Legal Foundation — IRC § 162(a)

The authority for deducting business expenses comes from a single provision of the Internal Revenue Code. IRC § 162(a) states that a taxpayer may deduct "all the ordinary and necessary expenses paid or incurred during the taxable year in carrying on any trade or business." That sentence is the entire foundation. Everything else — every publication, every IRS guidance document, every court case — is an interpretation of those words.

The Two-Part Test — IRC § 162(a)
Ordinary + Necessary = Deductible Business Expense
Ordinary: The expense is common and accepted in your trade or industry. It doesn't have to occur frequently — it just has to be the kind of expense that businesses like yours routinely incur. A restaurant buying cooking equipment is ordinary. A restaurant buying a private jet is not.

Necessary: The expense is helpful and appropriate for your business. The IRS does not require that it be indispensable — only that it serves a legitimate business purpose. Both conditions must be satisfied. An expense that is ordinary but not necessary, or necessary but not ordinary, does not qualify.

The Supreme Court addressed these definitions directly in Welch v. Helvering, a foundational tax case that still shapes how the IRS and courts evaluate disputed deductions today. The court held that "ordinary" and "necessary" carry different meanings — both of which must be satisfied independently. An expense that passes one test but not the other is not deductible.

One additional requirement that the statute implies and the IRS enforces: the amount must be reasonable. An otherwise qualifying expense that is lavish or extravagant relative to the business purpose may be partially or fully disallowed.

What Qualifies — The Major Categories

IRS Publication 334 (the current replacement for the discontinued Publication 535) and the Schedule C instructions lay out the most common categories of deductible business expenses. For most small businesses and self-employed owners filing Schedule C, these are the core deductions:

Advertising and Marketing
Fully Deductible
Costs to promote your business — digital advertising, print, signage, website development, social media promotion, business cards, and promotional materials. These are ordinary and necessary for virtually any business. The expense must be for business promotion, not personal image. Lending angle: Marketing spend reduces net income on your tax return. A lender evaluating your cash flow will see this as an operating expense — which is appropriate, since it's a real cost of running the business.
Employee Wages and Compensation
Fully Deductible — Must Be Reasonable
Salaries, wages, bonuses, and other compensation paid to employees are deductible — provided the compensation is reasonable and actually paid for services rendered. Compensation to owners is treated differently depending on business structure. S-corp shareholders who work in the business must pay themselves a reasonable salary before taking distributions. Lending angle: Owner compensation paid through the business reduces reported net income. Lenders underwriting a business owned by a working owner will often add back above-market owner compensation to normalize the cash flow picture.
Rent and Lease Payments
Fully Deductible — Business Use Only
Rent paid for office space, retail space, warehouse, or equipment used in the business is deductible. If you rent property that you also use personally, only the business-use portion qualifies. Prepaid rent paid in advance is generally deductible only in the year it applies. Lending angle: Rent is a fixed operating cost lenders treat as a recurring obligation. In a global cash flow analysis, a lender may ask whether lease payments continue or whether you own the property outright — both affect the cash flow picture differently.
Business Insurance Premiums
Fully Deductible
Premiums paid for insurance that protects your business are ordinary and necessary expenses. This includes general liability insurance, commercial property insurance, professional liability (errors and omissions), business interruption insurance, and workers' compensation. Personal life insurance where the business is the beneficiary is generally not deductible. Lending angle: Lenders routinely verify that the business carries adequate insurance as part of underwriting — particularly for SBA loans, which require hazard insurance on collateral. Your insurance premiums on the tax return are evidence of coverage.
Interest on Business Loans
Deductible — Subject to Limitations
Interest paid on debt used for business purposes is generally deductible under IRC § 163. This includes interest on business lines of credit, equipment loans, commercial mortgages, and SBA loans. The debt must be genuinely business-related — interest on personal loans used for personal purposes is not deductible even if you're self-employed. Note: The Tax Cuts and Jobs Act introduced a business interest limitation for larger businesses; most small businesses are exempt under the small business exception. Beginning in 2025, interest on qualified passenger vehicle loans may also be deductible. Lending angle: This is the most direct connection between your tax return and your debt service. Interest you're already paying appears on your tax return — and that existing debt service reduces the cash flow available for a new loan. Lenders calculate your existing debt obligations directly from this line.
Professional Fees
Fully Deductible
Fees paid to attorneys, accountants, consultants, and other professionals for services directly related to the business are ordinary and necessary expenses. Per the Schedule C instructions, this includes fees for tax advice related to the business and preparation of business tax forms, as well as fees incurred resolving tax deficiencies related to the business. Fees for purely personal legal or financial matters are not deductible. Lending angle: Lenders reviewing your tax return may see professional fees as a one-time or recurring cost. A large legal fee from a one-time matter can suppress net income in a single year — be prepared to explain it if it's in a year the lender is using for DSCR analysis.
Business Meals
50% Deductible — Strict Requirements
Meals with current or prospective clients, customers, or business contacts are 50% deductible — provided the expense is ordinary and necessary, not lavish or extravagant, and you or an employee was present. Entertainment expenses (sporting events, concerts, golf) are generally not deductible since the Tax Cuts and Jobs Act eliminated the entertainment deduction. The meal and the entertainment must be separated — a business dinner before a ball game is 50% deductible; the game tickets are not. Lending angle: Meal deductions are a common audit target because they are easy to inflate and hard to substantiate. Lenders don't typically focus on this line — but if your Schedule C shows unusually high meals relative to revenue, it can raise questions.
Vehicle and Mileage Expenses
Deductible — Two Methods, Choose One
Business use of a vehicle can be deducted using either the standard mileage rate or the actual expense method. For 2025, the standard mileage rate is 70 cents per mile for business use — up from prior years. Under the actual expense method, you deduct the business-use percentage of actual costs: gas, insurance, repairs, registration, and depreciation. You cannot switch from actual expense back to standard mileage after the first year if you used the actual method. Lending angle: Vehicle expenses appear on Schedule C and reduce net income. Lenders don't adjust for vehicle expenses the way they do for depreciation — vehicle costs are treated as a real operating expense.

What Does Not Qualify — Common Mistakes

The ordinary and necessary standard disqualifies more than people expect. These are the most common categories of expenses that business owners incorrectly deduct:

Expense Why It Fails the Test Lending Implication
Personal expenses run through the business Not ordinary or necessary for the trade or business. Personal clothing, personal meals, personal travel are not deductible even if you paid with a business card. Inflates expenses artificially, suppressing net income. Lenders sometimes spot this on unusual Schedule C line items relative to industry norms.
Capital expenditures (equipment, property) Capital costs must be depreciated over time under MACRS rules — they are not immediately deductible as ordinary expenses (unless Section 179 or bonus depreciation is elected). This is the depreciation addback lenders make. See below.
Fines and penalties paid to the government IRC § 162(f) explicitly prohibits deducting fines or penalties paid to a government entity for violating the law. OSHA fines, environmental penalties, and traffic violations are not deductible. No direct impact on DSCR — these are typically small amounts.
Lobbying and political contributions IRC § 162(e) disallows deductions for lobbying expenses and political contributions. Dues to organizations that conduct lobbying may be partially disallowed. Minimal lending impact for most small businesses.
Startup costs (in year incurred) Startup costs incurred before the business opens are not immediately deductible — they must be amortized over 180 months, with up to $5,000 deductible in the first year (phasing out above $50,000 in startup costs). In year one, a new business's net income is often depressed by startup cost amortization. Lenders underwriting newer businesses factor this in.

The Cash vs. Accrual Timing Question

When you can deduct an expense depends on your accounting method — and this is a detail that has real implications for both your tax bill and your loan application.

Accounting Method Determines When You Deduct
Cash Method: Deduct when paid  |  Accrual Method: Deduct when incurred
Under the cash method, you deduct an expense in the year you actually pay it — even if the service was performed in a prior year. Under the accrual method, you deduct expenses when you become legally obligated to pay them, regardless of when payment is made. Most small businesses use the cash method. Expenses paid in advance generally must be allocated to the years they apply, even under the cash method.

This matters for lending because a lender typically reviews two to three years of tax returns. A business that accelerated deductions into one year (by prepaying expenses under the cash method, for example) may show a suppressed income year that skews the lender's average. If this happened in your tax history, be prepared to explain it.

The Lending Dimension — How Business Deductions Affect Your Loan Application

This is where most business owners discover something their accountant never mentioned: the tax strategy that saved you the most money last year may also be the thing making it harder to get a loan this year.

The Net Income Problem

Lenders use your tax return — specifically your net income from Schedule C, or your business's net income from a partnership or corporate return — as the foundation for calculating your debt service coverage ratio (DSCR). DSCR measures whether your business generates enough income to cover its debt payments. The SBA's minimum DSCR for most loan programs is 1.15x — meaning your business must generate at least $1.15 in income for every $1.00 of annual debt service.

Every legitimate deduction you take reduces that net income figure. If your net income is low because you've aggressively deducted ordinary and necessary expenses, your DSCR will be lower — even if your actual cash flow is strong.

What Lenders Add Back

Sophisticated commercial lenders don't stop at net income. They perform an addback analysis to reconstruct your actual cash flow by adding back non-cash expenses and one-time items. The most common addback is depreciation — which is a non-cash deduction that reduces net income without reducing actual cash in the business.

Schedule C Net Income vs. Lender Cash Flow — A Real Example
Gross revenue $480,000
Total ordinary and necessary expenses deducted ($410,000)
Net income (as reported on Schedule C) $70,000
Add back: Depreciation (non-cash) + $55,000
Add back: Amortization (non-cash) + $8,000
Add back: Interest expense (already in debt service) + $22,000
Adjusted cash flow (what lender uses) $155,000
Annual debt service (existing + proposed) $110,000
DSCR 1.41x ✅

A business showing $70,000 in net income might appear to be borderline for a large loan. But once the lender adds back depreciation, amortization, and interest, the adjusted cash flow of $155,000 produces a DSCR of 1.41x — comfortably above the SBA minimum of 1.15x. This is why knowing your addback number matters before you walk into a loan application.

Expenses Lenders Do Not Add Back

Not every deduction gets added back. Legitimate cash operating expenses — rent, payroll, insurance, advertising, professional fees — stay in the calculation. These represent real dollars leaving the business and reduce the cash available for debt service. A lender who added back your rent expense to inflate your DSCR would be doing you no favors; the rent bill still comes due every month.

The Deduction Trap — When Tax Strategy Conflicts with Loan Readiness

Some business owners maximize deductions every year without thinking about the downstream lending impact. If you plan to apply for a significant loan in the next 12 to 24 months, that timing matters. Aggressively deducting expenses in the years a lender will review reduces your reported net income and can lower your DSCR — even if your actual cash flow is healthy. This isn't an argument against taking legitimate deductions; it's an argument for understanding how lenders will read your return before you file it. A conversation with both your accountant and a lender before year-end can help you make informed decisions.

The QBI Deduction — A 2025 Update Worth Knowing

One additional deduction that sits alongside the ordinary and necessary framework is the Qualified Business Income (QBI) deduction, established under the Tax Cuts and Jobs Act and now made permanent under the One Big Beautiful Bill Act signed in 2025. Eligible self-employed individuals and pass-through business owners can deduct up to 20% of qualified business income from federal taxable income — subject to income thresholds and business type limitations.

The QBI deduction does not reduce Schedule C net income. It is taken on the personal return below the line and does not affect the net income figure lenders see when they pull your tax return for underwriting. This is actually favorable from a loan readiness standpoint: you get the tax benefit without reducing the income figure your lender uses for DSCR.

Documentation Is Not Optional
The IRS places the burden of substantiation squarely on the taxpayer. An expense that qualifies as ordinary and necessary is still disallowed if you cannot prove it. That means receipts, invoices, bank statements, and for meals and vehicle expenses, contemporaneous logs showing the business purpose. Per the Tax Court in Sherman, T.C. Memo. 2023-63, taxpayers must substantiate not just the amount of a deduction but also that the purpose was ordinary and necessary to the business. Keep records for at least three years from the date you file — seven years if you claim a loss from worthless securities or bad debt.

Pulling It Together — What to Know Before You File and Before You Apply

Business expense deductions are one of the most powerful tools available to small business owners. The ordinary and necessary standard under IRC § 162(a) covers a broad range of legitimate costs — advertising, payroll, rent, insurance, interest, professional fees, vehicle use, and more — and taking full advantage of these deductions is simply good tax planning.

The discipline is in understanding two things simultaneously: what the IRS allows, and how a lender will read the result. A tax return that reflects aggressive but legitimate deductions may look lean to a lender who doesn't perform a thorough addback analysis. Know your adjusted cash flow number — your net income plus depreciation, amortization, and interest — before you apply for any significant financing. That number is what a sophisticated commercial lender is actually evaluating.

If you're planning to apply for a business loan in the near term, consider reviewing your prior-year tax returns through a lender's eyes before your next filing. The decisions you make on deductions today show up in the underwriting file tomorrow.

See How Your Tax Return Looks to a Lender

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This article is for educational purposes only and does not constitute tax or legal advice. Business expense rules are fact-specific and subject to change. IRS Publication 535 (Business Expenses) was discontinued after tax year 2022; current guidance is available in IRS Publication 334 (Tax Guide for Small Business) and at IRS.gov. The Qualified Business Income deduction rules were made permanent under the One Big Beautiful Bill Act (P.L. 119-21) signed in 2025. All figures and rates referenced reflect 2025 tax year guidance per IRS.gov. Consult a qualified tax professional before making deduction decisions.

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