A write-off in accounting is either a business expense you subtract from income before tax is calculated, or a bookkeeping entry that removes the value of an asset that has become worthless. Both lower what a business owes, but neither cuts the tax bill dollar-for-dollar. A $10,000 write-off saves a C corporation $2,100 at the current 21% federal rate; a sole proprietor in the 24% bracket saves about $2,400 in income tax on the same amount. The savings equal the write-off multiplied by your tax rate, not the write-off itself.
That distinction matters because “write-off” gets used loosely. In careful accounting, the word covers two related actions with different mechanics, and mixing them up is the fastest way to misunderstand what a deduction is actually worth.
The Two Kinds of Write-Offs
The first kind is a tax deduction: an ordinary operating cost — rent, advertising, supplies, professional fees — subtracted from gross revenue before the tax rate is applied. This is what most people mean when they say a business “wrote it off.”
The second kind is a balance-sheet adjustment: reducing or removing the recorded value of an asset that has lost its worth. An invoice from a customer who has gone bankrupt, inventory destroyed in a flood, equipment that no longer functions. The asset comes off the books, and the loss becomes deductible in the year it’s recognized.
A write-off is not a tax credit. Credits cut the final tax bill dollar for dollar. Deductions cut the income the tax rate applies to. A first-time business owner who hears “you can write that off” and expects the government to reimburse the full cost has misread the math.
The Ordinary and Necessary Standard
Business expense deductions rest on IRC Section 162, which allows a deduction for costs that are ordinary and necessary for carrying on a 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 producing income — the IRS has long held it does not have to mean indispensable.
The expense also has to be reasonable in amount. Auditors look hard at costs that seem inflated or that blend personal and business use. The burden of proof sits with you: claim it, and you need to be able to show it was real, business-related, and appropriately sized.
Common Business Write-Offs
Most routine operating costs are fully deductible in the year you pay them. Advertising, office supplies, rent, utilities, software subscriptions, professional fees paid to accountants or attorneys, and business insurance premiums all qualify. For sole proprietors and single-member LLCs, these flow through Schedule C and directly reduce net profit.
Vehicle Expenses
Business use of a vehicle can be deducted two ways. The standard mileage rate for 2026 is 72.5 cents per mile.2Internal Revenue Service. IRS Sets Business Standard Mileage Rate Or you can track actual costs — fuel, maintenance, insurance, registration — and deduct the business-use percentage. If you own the vehicle and want the standard rate, you have to elect it in the first year the car is available for business. For leased vehicles, whichever method you pick has to stay in place for the entire lease.
Home Office
A dedicated home workspace used exclusively and regularly as your principal place of business, or as a place where you meet clients, qualifies for the home office deduction. The simplified method gives you a flat $5 per square foot up to 300 square feet, capped at $1,500.3Internal Revenue Service. Simplified Option for Home Office Deduction The regular method uses the actual percentage of your home the office occupies, applied to rent or mortgage interest, utilities, and insurance. Bigger spaces do better under the regular method; simpler record-keeping wins under the flat rate.
Business Travel and Meals
Travel costs for a trip primarily for business — airfare, lodging, car rentals, and similar — are fully deductible.4Internal Revenue Service. Topic No. 511 – Business Travel Expenses Business meals are deductible at 50% when someone from your business is present and the meal is not lavish.5Internal Revenue Service. Publication 463 – Travel, Gift, and Car Expenses The temporary 100% deduction for restaurant meals in 2021 and 2022 has expired. The 50% cap applies for 2026.
Business Gifts
Gifts to clients, vendors, or business contacts are deductible, but only up to $25 per recipient per year.6Office of the Law Revision Counsel. 26 U.S. Code 274 – Disallowance of Certain Entertainment, Amusement, Recreation, and Travel Expenses That ceiling has not moved since 1962. Engraving, wrapping, and shipping do not count against the cap. Promotional items under $4 that carry your business name — pens, calendars, magnets — are excluded entirely.
Self-Employed Health Insurance
Self-employed people who are not eligible for coverage through a spouse’s employer plan can deduct 100% of premiums for health, dental, and long-term care insurance for themselves, a spouse, and dependents.7Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes) It comes off gross income on your personal return rather than Schedule C, so it lowers income tax but not self-employment tax.
What You Cannot Write Off
Several categories are barred outright, and claiming them draws attention fast.
- Government fines and penalties — traffic tickets, OSHA fines, environmental penalties — cannot be deducted.8eCFR. 26 CFR 1.162-21 – Denial of Deduction for Certain Fines, Penalties, and Other Amounts
- Political contributions and lobbying expenses are never deductible under IRC Section 162(e).9Internal Revenue Service. Nondeductible Lobbying and Political Expenditures
- Commuting from home to a regular workplace is a personal expense. Only trips from your workplace to a second business location, or travel away from your tax home, qualify.
- Country club, social club, and athletic facility dues do not qualify, even if you meet clients there.
- Personal expenses do not become deductible because business gets discussed. Clothing that can be worn outside work, personal grooming, and lavish entertainment stay personal.
Mixed-use costs — a phone used for both personal and business calls, a car driven to job sites and to the grocery store — are deductible only for the business portion, and only if you have contemporaneous records that back up the split. Most audit disputes over deductions happen right at this line.
Immediate Expensing vs. Depreciation
Whether a cost gets deducted in one year or spread across many depends on how long the benefit lasts. Short-lived items like rent and supplies come off in the year paid. Assets with a lasting benefit — a delivery truck, manufacturing equipment, a patent — have to be capitalized: recorded on the balance sheet, then written down gradually through depreciation (for tangible assets) or amortization (for intangibles).
MACRS Depreciation
Property placed in service after 1986 is depreciated under the Modified Accelerated Cost Recovery System, which assigns each asset type a set recovery period: five years for computers, seven for office furniture, 39 for commercial buildings, and so on.10Internal Revenue Service. Topic No. 704, Depreciation Each year you deduct a fraction of the cost until the asset is written down to zero.
Section 179
Section 179 lets you deduct the full price of qualifying equipment, vehicles, software, and certain improvements in the year they go into service. For 2026, the maximum Section 179 deduction is $2,560,000, phasing out dollar for dollar once total equipment purchases pass $4,090,000.11Internal Revenue Service. Instructions for Form 4562 The deduction cannot exceed your taxable business income for the year, so Section 179 cannot create or deepen a loss.
Bonus Depreciation
Bonus depreciation works alongside Section 179 but has no taxable-income cap, meaning it can produce a net operating loss. The One Big Beautiful Bill Act, signed in July 2025, reversed the scheduled phaseout and permanently restored 100% bonus depreciation for qualified property acquired after January 19, 2025.12Internal Revenue Service. Treasury, IRS Issue Guidance on the Additional First Year Depreciation Deduction Amended as Part of the One Big Beautiful Bill For most businesses buying equipment in 2026, the entire cost can come off in year one.
Amortization of Intangibles
Patents, trademarks, customer lists, and goodwill acquired in a business purchase get written off through amortization. IRC Section 197 spreads these costs evenly over 15 years, starting in the month of acquisition.13Office of the Law Revision Counsel. 26 U.S. Code 197 – Amortization of Goodwill and Certain Other Intangibles Intangibles do not qualify for Section 179 or bonus depreciation.
Writing Off Bad Debts
When a customer owes money and collection has become impossible, the receivable can be written off as a bad debt. You have to be able to show the debt is genuinely worthless — that you took reasonable collection steps and concluded pursuing more would be futile.14Internal Revenue Service. Topic No. 453, Bad Debt Deduction A court judgment is not required.
Business bad debts can be deducted in full or in part. The amount has to have been previously included in gross income, which happens automatically for accrual-method businesses that recognized the revenue when the invoice went out. Cash-basis businesses generally cannot deduct unpaid invoices, because the income was never recorded. Timing is strict: the deduction has to be taken in the year the debt becomes worthless, and waiting too long can forfeit it.
How a Write-Off Actually Reduces Your Tax Bill
For a sole proprietor or independent contractor, each qualified write-off reduces net profit on Schedule C, which flows to Form 1040. That lower net profit reduces two taxes at once: federal income tax at your marginal rate, and self-employment tax.
Self-employment tax funds Social Security and Medicare at a combined 15.3% — 12.4% for Social Security and 2.9% for Medicare — but applies to 92.35% of net earnings rather than the full amount.15Internal Revenue Service. Topic No. 554, Self-Employment Tax Half of the self-employment tax comes off gross income as an adjustment, which shaves a bit more off income tax.
The rough math: a self-employed filer in the 24% bracket who finds $10,000 in legitimate write-offs cuts income tax by about $2,400 and self-employment tax by roughly $1,400. That is about $3,800 back — real savings, but a long way from $10,000. Anyone claiming a write-off “pays for itself” is misdescribing how deductions work.
C corporations run differently. Business income is taxed at a flat 21%, so each dollar of write-off saves 21 cents at the corporate level.16Worldwide Tax Summaries. United States Corporate – Taxes on Corporate Income There is no self-employment tax on corporate income, though owners who work in the business pay payroll taxes on their wages.
Record-Keeping
Every deduction needs documentation. Receipts, invoices, bank statements, and contemporaneous logs showing date, amount, and business purpose. An estimate does not survive an audit. The IRS can disallow anything you cannot substantiate, and the adjustment comes with interest and possible penalties.
Keep supporting records at least three years from the date the return was filed.17Internal Revenue Service. How Long Should I Keep Records? Six years if the IRS suspects you underreported income by more than 25%. Seven years for bad debt or worthless securities deductions. For depreciable property, hold onto purchase records for the life of the asset plus three years after disposal. Employment tax records — wages, benefits, payroll taxes — carry their own four-year retention period from the date the tax was due or paid, whichever is later.