Disallowable expenses are business costs the IRS will not let you subtract from taxable income, even when they appear on your books as legitimate expenses. Some are permanently off-limits, like fines, bribes, lobbying, entertainment, and club dues. Others are only partly deductible, like business meals and the personal share of a vehicle you also use for work. Treating a disallowed cost as a deduction leads to underreported tax, interest, and penalties, so the categories below are worth knowing before you file rather than after an audit notice arrives.
What Makes an Expense Disallowable
Every business deduction has to clear Section 162(a) of the Internal Revenue Code, which allows a write-off for costs that are 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 for the business, though not strictly essential. An expense that fails either test is disallowed from the start.
Beyond that threshold, the cost has to be genuinely tied to business activity. Personal expenses are never deductible, even when they overlap with work. Your daily commute from home to a fixed office, for instance, is personal no matter how far you drive. The line between personal and business spending is one of the most heavily audited areas of the tax code, and if you cannot show an expense served the business rather than you personally, the IRS will add it back to income.
A separate category causes confusion but is not truly disallowed: capital expenditures. When you buy something with a useful life beyond the current year (equipment, real estate, intellectual property) the cost is recovered gradually through depreciation or amortization rather than written off in full the year you pay it.2Internal Revenue Service. About Form 4562, Depreciation and Amortization A $200,000 machine might depreciate over five or seven years. Accelerated and bonus depreciation can front-load some of that recovery, but the full deduction still arrives on a timeline, not all at once.
Expenses You Can Never Deduct
The following costs are permanently nondeductible. However directly they relate to the business, they never reduce taxable income, and they have to be added back to book income when you calculate what you owe.
Fines and Penalties
Any amount paid to a government or governmental entity for violating a law, or for the investigation of a potential violation, is nondeductible.3Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses – Section: 162(f) That covers traffic tickets, regulatory fines, OSHA penalties, environmental violations, and civil penalties from agencies like the SEC. The tax code does not subsidize lawbreaking.
A narrow exception exists for amounts that qualify as restitution or payments made to come into compliance with the law. If a settlement agreement specifically identifies part of the payment as restitution for harm caused by the violation, that portion may be deductible, but the taxpayer must establish that the payment genuinely is restitution and the agreement must label it as such. Reimbursing the government for the cost of its investigation does not qualify.
Bribes and Illegal Payments
Illegal bribes and kickbacks are nondeductible whether they go to a government official or a private party.4eCFR. 26 CFR 1.162-18 – Illegal Bribes and Kickbacks For payments to foreign officials, the test is whether the payment would be unlawful under the Foreign Corrupt Practices Act. For payments to private individuals, the deduction is denied if the payment subjects the payor to a criminal penalty or the loss of a business license under federal or state law.
Healthcare businesses face a stricter rule. Any kickback, rebate, or bribe made by a healthcare provider in connection with services paid for by Medicare, Medicaid, or other federally funded programs is nondeductible, whether or not the payment is technically illegal. Payments for patient referrals fall squarely within this prohibition.
Lobbying and Political Spending
You cannot deduct expenses for influencing legislation, participating in political campaigns, swaying the general public on elections or referendums, or communicating with executive branch officials to influence their actions.5Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses – Section: 162(e) Direct campaign contributions, fundraising costs, and payments to political action committees all fall within this rule.
There is a small de minimis carve-out: if your total in-house lobbying expenditures for the year stay under $2,000, they remain deductible. Cross that threshold and the entire amount becomes nondeductible. The $2,000 limit does not include payments to outside lobbyists or dues to organizations that allocate a portion toward lobbying; both are disallowed regardless of amount.6Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses – Section: 162(e)(4)(B)
Entertainment and Club Dues
The Tax Cuts and Jobs Act eliminated the entertainment deduction starting in 2018.7Internal Revenue Service. Tax Cuts and Jobs Act: A Comparison for Businesses Costs for activities considered entertainment, amusement, or recreation are fully disallowed, even when the activity is tied to a business discussion. Sporting event tickets, golf outings, client concert tickets, and theater performances all fail the test.
Club membership dues are separately and permanently disallowed under a provision that predates the TCJA. No deduction is allowed for dues paid to any club organized for business, pleasure, recreation, or social purposes.8Office 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. Business meals are handled differently and appear in the next section.
Life Insurance Premiums (When the Business Benefits)
Premiums on a life insurance policy covering an officer, employee, or any person with a financial interest in the business are nondeductible if your business is directly or indirectly a beneficiary.9Office of the Law Revision Counsel. 26 USC 264 – Certain Amounts Paid in Connection With Insurance Contracts This commonly affects key-person policies where the company owns the policy and would collect the death benefit.
The rule does not apply when the business is not a beneficiary. Life insurance premiums paid as part of an employee’s compensation package, with the employee or their family as beneficiary, are deductible as ordinary compensation so long as total compensation remains reasonable.10eCFR. 26 CFR 1.264-1 – Premiums on Life Insurance Taken Out in a Trade or Business
Costs Tied to Tax-Exempt Income
If you earn income that is wholly exempt from federal tax, you cannot deduct the expenses attributable to producing it. The classic case is municipal bond interest: the interest is tax-free, so any related costs, including interest on debt used to buy the bonds, are nondeductible.11Office of the Law Revision Counsel. 26 USC 265 – Expenses and Interest Relating to Tax-Exempt Income The IRS will not let you benefit from the exemption on one side while deducting on the other.
Personal Costs With Incidental Business Benefit
Expenses that serve a personal purpose stay disallowed even when there is some business benefit. Work clothing is deductible only when it is not suitable for everyday wear and is required as a condition of employment, like a hard hat or a branded uniform. Haircuts, dry cleaning for ordinary business attire, and gym memberships are personal costs the tax code does not reach. Mixed-use expenses require allocation, and the personal portion is always disallowed. That allocation principle drives the next set of rules.
Expenses You Can Deduct Only in Part
Some costs are partially deductible. The tax code lets you write off a percentage and permanently disallows the rest. Documentation is what makes the deductible share stick.
Business Meals (50%)
You can deduct only 50% of the cost of qualifying business meals.12Office of the Law Revision Counsel. 26 USC 274 – Disallowance of Certain Entertainment, Etc., Expenses – Section: 274(n) The other half is permanently disallowed. To claim even the 50%, the meal cannot be lavish or extravagant, you or an employee must be present when the food is served, and a current or potential business contact must be involved for a legitimate business purpose.13Internal Revenue Service. Income and Expenses FAQ If you take a client to dinner and then to a concert, the meal and the entertainment have to be billed separately. The meal gets the 50%; the concert tickets get nothing.
Business Use of a Vehicle
Only the business-use share of vehicle costs is deductible. The personal-use share is fully disallowed. You have two methods:
- Standard mileage rate. For 2026, the IRS rate is 72.5 cents per business mile. Multiply total business miles by that rate.14Internal 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 by the fraction of miles driven for business versus total miles.
Either method requires a contemporaneous mileage log recording date, destination, and business purpose for every trip. Without the log, the IRS will disallow the entire vehicle deduction, not just the personal share. Vehicle claims collapse at audit more often from missing logs than from bad math.
Home Office
If you use part of your home exclusively and regularly as your principal place of business or a space to meet clients, you can allocate a portion of mortgage interest, utilities, insurance, and repairs to the business. The deductible percentage equals the office’s square footage divided by the home’s total square footage. The IRS also offers a simplified method of $5 per square foot of office space, capped at 300 square feet, for a maximum deduction of $1,500.15Internal Revenue Service. Simplified Option for Home Office Deduction The word “exclusively” matters. If the office doubles as a guest bedroom, the entire deduction is disallowed.
Startup Costs
Costs incurred to investigate or launch a new business are not 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 allowance is reduced dollar-for-dollar once total startup costs exceed $50,000. At $55,000 or more, the first-year deduction drops to zero.16Office of the Law Revision Counsel. 26 USC 195 – Start-Up Expenditures Whatever you cannot take upfront is amortized ratably over 180 months starting from the month the business opens. A $60,000 launch deducts nothing in year one and spreads the full amount across 15 years.
Executive Pay Above $1 Million
Publicly traded corporations cannot deduct more than $1 million per year in compensation paid to certain top executives.17Internal Revenue Service. IRS Publication 6014 – Section 162(m) Audit Technique Guide Compensation above the cap 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-compensated officers whose pay must be reported to shareholders. Anyone who held one of those positions in any tax year after 2016 remains a covered employee permanently, even after leaving the role.18Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses – Section: 162(m) The cap applies to all forms of pay: salary, bonuses, commissions, and stock-based compensation. The pre-TCJA exception for performance-based pay was repealed for tax years beginning after 2017.
Losses Between Related Parties
Losses on sales or exchanges between related parties are completely disallowed. Sell property at a loss to a family member, a corporation you control, a trust you established, or any of several other related-party combinations defined by the tax code, and the loss is gone.19Office of the Law Revision Counsel. 26 USC 267 – Losses, Expenses, and Interest With Respect to Transactions Between Related Taxpayers “Related parties” is defined broadly and includes:
- Family members: siblings, spouses, ancestors, and lineal descendants
- An individual and a corporation in which 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 rules widen the net further. Stock owned by your spouse, children, grandchildren, or parents counts as yours when measuring the 50% threshold, so transactions that look arm’s-length on paper can still be caught.
Reporting Disallowed Amounts on Your Return
Financial statements prepared for shareholders include every expense you incurred, including the ones the IRS rejects. To get to taxable income, you add every disallowed amount back to book income. The differences fall into two groups: permanent, like fines and entertainment, which never reverse; and temporary, like depreciation timing, which reverse as assets are fully written off.
C corporations document the reconciliation on Schedule M-1 or Schedule M-3 of their return. Schedule M-3 is required when total assets reach $10 million or more; smaller corporations use the simpler Schedule M-1.20Internal Revenue Service. Schedules M-1 and M-2 (Form 1120-F) Both schedules give a line-by-line breakdown of each adjustment, and the IRS scrutinizes them heavily. Sloppy reconciliation is one of the faster paths to an audit.
Track nondeductible costs in separate general ledger accounts throughout the year rather than reconstructing them at filing time. A dedicated “Non-Deductible Entertainment” or “Non-Deductible Fines” account makes the year-end add-back routine. Keep invoices, receipts, and documentation even for expenses you know are disallowed. If the IRS challenges any item, you carry the burden of proving the expense was real and categorized correctly.