Disallowable expenses are business costs the IRS refuses to let you subtract from taxable income, even when they sit on your books as legitimate business spending. Some are blocked permanently, such as fines, bribes, entertainment, and club dues. Others are only partly blocked, such as business meals, where you lose half the deduction, or mixed-use vehicles, where the personal miles fall away. A third group isn’t disallowed forever but can’t be written off in the year you paid, which includes capital purchases and most startup costs. Getting these categories wrong understates your tax liability and invites penalties and interest.
Why an Expense Gets Disallowed in the First Place
Every business deduction has to clear Section 162(a): the expense must be both “ordinary” and “necessary” in carrying on a trade or business.1Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses Ordinary means common and accepted in your industry. Necessary means helpful and appropriate, not indispensable. Fail either prong and the expense is gone.
Even expenses that pass that test have to be genuinely connected to business activity. Personal spending is never deductible, no matter how the cost happens to overlap with work. Your daily commute is the classic example: it’s a personal cost regardless of the distance. The line between personal and business is one of the most heavily audited areas of the code, and if you can’t show the money served the business rather than you, the IRS adds it back.
Expenses That Are Permanently Nondeductible
These costs never reduce taxable income, no matter how directly they connect to the business. On the tax return, they get added back to book income.
Fines and Penalties Paid to the Government
Any amount paid to a government for violating a law, or even for the investigation of a possible violation, is nondeductible.2Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses – Section: 162(f) Traffic tickets, regulatory fines, OSHA penalties, environmental violations, and civil penalties from agencies like the SEC all sit in this bucket. The tax code doesn’t subsidize lawbreaking.
There is a narrow exception. If a settlement agreement specifically identifies part of the payment as restitution for harm caused by the violation, or as a payment to bring the taxpayer into compliance with the law, that portion may be deductible. The taxpayer has to establish the payment genuinely qualifies, and the agreement has to label it that way. Reimbursing the government for the cost of its investigation doesn’t qualify.
Bribes and Illegal Kickbacks
Illegal bribes and kickbacks are nondeductible, whether they go to a government official or a private party.3eCFR. 26 CFR 1.162-18 – Illegal Bribes and Kickbacks For payments to foreign officials, the test is whether the payment would violate the Foreign Corrupt Practices Act. For payments to private parties, the deduction is denied when the payment could bring a criminal penalty or the loss of a business license under federal or state law. Kickbacks, rebates, and bribes by healthcare providers tied to services paid for by Medicare, Medicaid, or other federally funded programs are separately disallowed, whether or not technically illegal.
Lobbying and Political Spending
You cannot deduct expenses for influencing legislation, participating in political campaigns, swaying the public on elections or referendums, or communicating with executive branch officials to influence their actions.4Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses – Section: 162(e) Campaign contributions, fundraising costs, and payments to political action committees are all blocked.
One small carve-out: in-house lobbying stays deductible if total in-house lobbying for the year is under $2,000. Cross that line and the entire amount becomes nondeductible.5Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses – Section: 162(e)(4)(B) The $2,000 limit doesn’t cover outside lobbyists or association dues allocated to lobbying, which are disallowed regardless of amount.
Entertainment and Club Dues
The Tax Cuts and Jobs Act eliminated the entertainment deduction starting in 2018.6Internal Revenue Service. Tax Cuts and Jobs Act: A Comparison for Businesses Costs treated as entertainment, amusement, or recreation are fully disallowed, even when the activity ties directly to a business discussion. Sports tickets, golf outings, concert tickets for clients, and theater performances all fail.
Club dues sit under a separate, older prohibition. No deduction is allowed for dues to any club organized for business, pleasure, recreation, or social purposes.7Office of the Law Revision Counsel. 26 USC 274 – Disallowance of Certain Entertainment, Etc., Expenses – Section: 274(a)(3) Country clubs, golf clubs, airline lounges, and social clubs all fall under this rule.
Life Insurance Premiums When the Business Is the Beneficiary
Premiums on a life insurance policy covering an officer, employee, or anyone financially interested in the business are nondeductible if the business is directly or indirectly a beneficiary.8Office of the Law Revision Counsel. 26 USC 264 – Certain Amounts Paid in Connection With Insurance Contracts Key-person policies where the company owns the coverage and would collect the death benefit are the common case. When the business isn’t the beneficiary and the premium is paid as part of an employee’s compensation with the employee or their family collecting, the premium is deductible as ordinary compensation, provided total compensation stays reasonable.9eCFR. 26 CFR 1.264-1 – Premiums on Life Insurance Taken Out in a Trade or Business
Expenses Tied to Tax-Exempt Income
Expenses allocable to income that is wholly exempt from federal tax are nondeductible.10Office of the Law Revision Counsel. 26 USC 265 – Expenses and Interest Relating to Tax-Exempt Income The most common case: interest on debt used to buy municipal bonds, where the bond interest itself is tax-free. You can’t take the exemption on one side and deduct the costs of earning it on the other.
Personal Costs, Even Ones That Help at Work
Work clothing is deductible only if it isn’t suitable for everyday wear and is required as a condition of employment, such as a hard hat or a branded uniform. Haircuts, dry cleaning for ordinary business attire, and gym memberships are personal.
Executive Compensation Above $1 Million
Publicly traded corporations can’t deduct more than $1 million per year in compensation paid to certain top executives.11Internal Revenue Service. IRS Publication 6014 – Section 162(m) Audit Technique Guide Anything above that is permanently disallowed for the corporation, though the executive still owes income tax on the full amount. Covered employees include the principal executive officer, the principal financial officer, and the three next-highest-paid officers reported to shareholders; anyone who held one of those positions in any tax year after 2016 stays a covered employee permanently.12Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses – Section: 162(m) The cap covers salary, bonuses, commissions, and stock-based compensation alike.
Expenses That Are Only Partly Deductible
These items look deductible but the code permanently disallows a portion. The deductible share depends on documentation.
Business Meals
Only 50% of the cost of a business meal is deductible.13Office of the Law Revision Counsel. 26 USC 274 – Disallowance of Certain Entertainment, Etc., Expenses – Section: 274(n) The other half is gone. To claim even the 50%, the meal can’t be lavish or extravagant, you or an employee must be present when the food is served, and the meal has to involve a current or potential business contact for a legitimate business purpose.14Internal Revenue Service. Income and Expenses FAQ The temporary 100% deduction for restaurant meals during 2021 and 2022 expired on December 31, 2022; the 50% limitation applies for 2026. If you take a client to dinner and then a concert, bill the two separately. The meal gets 50%. The concert gets nothing.
Vehicle Use
Only the business-use share of vehicle costs is deductible. Two methods:
- Standard mileage rate. For 2026, the IRS rate is 72.5 cents per business mile. Multiply business miles by that rate.15Internal Revenue Service. IRS Sets 2026 Business Standard Mileage Rate at 72.5 Cents Per Mile
- Actual expenses. Add up gas, insurance, repairs, depreciation, and other vehicle costs, then multiply the total by business miles divided by total miles.
Either method requires a contemporaneous mileage log with date, destination, and business purpose for every trip. No log, no deduction, and the disallowance covers the whole claim, not just the personal share. This is where most vehicle deductions fall apart on audit.
Home Office
Use part of your home exclusively and regularly as your principal place of business or a client-meeting space, and you can allocate a share of household costs (mortgage interest, utilities, insurance, repairs) to the business. The deductible percentage is the office’s square footage over the home’s total square footage. The rest is personal. There’s also a simplified method: $5 per square foot up to 300 square feet, for a maximum of $1,500.16Internal Revenue Service. Simplified Option for Home Office Deduction “Exclusively” is strict. If the office doubles as a guest bedroom, the entire deduction is disallowed.
Costs You Deduct Later, Not Now
Some spending isn’t disallowed forever. It’s just not deductible in the year you paid.
Capital Expenditures
When you buy something with a useful life beyond the current year (equipment, real estate, intellectual property), the IRS treats the cost as a capital expenditure. You recover it over time through depreciation or amortization instead of writing off the whole amount now.17Internal Revenue Service. About Form 4562, Depreciation and Amortization A $200,000 machine might be depreciated over five or seven years. Accelerated depreciation and bonus depreciation can front-load the recovery, but the full purchase price still can’t be immediately expensed.
Startup Costs
Costs to investigate or launch a new business aren’t fully deductible in year one. You can elect to deduct up to $5,000 of startup expenses in the year the business begins, but that $5,000 shrinks dollar-for-dollar once total startup costs pass $50,000. At $55,000 or more, the first-year deduction is zero.18Office of the Law Revision Counsel. 26 USC 195 – Start-Up Expenditures Whatever you can’t take up front is amortized ratably over 180 months from the month the business begins operating. A business that spends $60,000 getting off the ground deducts nothing upfront and spreads the full $60,000 across 15 years.
Excess Business Losses
Non-corporate taxpayers (individuals, partners, S corporation shareholders) face a cap on how much business loss can offset other income in a single year. For 2025, the threshold is $313,000 for single filers and $626,000 for joint filers, adjusted annually for inflation.19Internal Revenue Service. 2025 Instructions for Form 461 A loss above the threshold isn’t lost permanently; it carries forward as a net operating loss. The rule stops high-income taxpayers from using large business losses to wipe out tax on wages or investment income in one year.
Losses on Sales to Related Parties
Sell property at a loss to a related party and the loss is completely disallowed.20Office of the Law Revision Counsel. 26 USC 267 – Losses, Expenses, and Interest With Respect to Transactions Between Related Taxpayers The related-party definition is broad:
- Family members: siblings, spouses, ancestors, and lineal descendants
- An individual and a corporation, when the individual owns more than 50% of the stock
- Two corporations in the same controlled group
- A grantor and a trust, or a trust and its beneficiaries
- A corporation and a partnership when the same persons own more than 50% of both
Constructive ownership widens the reach. Stock held by your spouse, children, grandchildren, or parents counts as yours when measuring the 50% threshold. Transactions that look arm’s-length on the surface can fall inside the rule once family networks get counted.
How Disallowed Amounts Show Up on the Return
Your financial statements include every expense, disallowed or not. Taxable income is what remains after you add the disallowed amounts back to book income. These add-backs split into two types: permanent differences, like fines and entertainment, which never reverse; and temporary differences, like depreciation timing, which reverse over the asset’s life.
C corporations report the reconciliation on Schedule M-1 or Schedule M-3. Schedule M-3 is required when total assets reach $10 million or more; smaller corporations use the simpler Schedule M-1.21Internal Revenue Service. Schedules M-1 and M-2 (Form 1120-F) Both schedules break out every adjustment line by line, and the IRS reviews them closely. Sloppy reconciliation is a fast path to audit.
The cleanest practice is to track nondeductible expenses in separate general ledger accounts throughout the year. A dedicated “Non-Deductible Entertainment” or “Non-Deductible Fines” account makes the year-end add-back straightforward. Keep the invoices, receipts, and documentation even for items you know are disallowed. If the IRS challenges anything, you carry the burden of proving the expense happened and belongs where you put it.