You can write off business expenses as a sole proprietor whenever they’re ordinary and necessary for your trade, and those deductions come off your income on Schedule C before either income tax or self-employment tax is calculated. Because a sole proprietorship isn’t a separate tax entity, every dollar of legitimate deduction lowers the number that flows to your personal return. For most self-employed people, working through these categories carefully is the single most valuable tax move of the year.
What Counts as a Deductible Business Expense
Federal tax law lets you deduct all “ordinary and necessary” expenses of carrying on a business.1Office of the Law Revision Counsel. 26 USC 162 – Trade or Business Expenses Ordinary means the expense is common and accepted in your line of work. Necessary means it’s helpful and appropriate. The expense doesn’t have to be indispensable; it just has to serve a real business purpose rather than a personal one.
The line between business and personal spending is strict. Flying to meet a client is deductible travel. Driving from your house to the same office every morning is personal commuting. When something is used for both, you deduct only the business share. A cell phone split evenly between work and personal calls is 50% deductible.
The Everyday Deductions Most Sole Proprietors Claim
Day-to-day operating costs are the most straightforward write-offs. Supplies consumed in the normal course of business (paper, cleaning products, raw materials) come straight off revenue. Advertising and marketing qualify as long as they’re aimed at attracting or keeping customers, whether that’s online ads, business cards, or a website. Fees paid to accountants, attorneys, or other professionals for business services are deductible in the year you pay them.
Insurance premiums that protect the business are generally deductible, including liability coverage, malpractice insurance, and property insurance on business assets. Rent, utilities, and dedicated internet or phone service for a business location separate from your home also qualify. Business travel expenses (airfare, lodging, ground transportation) are deductible when you travel overnight away from your tax home for business reasons, provided the costs aren’t extravagant.
Meals with a business purpose are 50% deductible.2Internal Revenue Service. Income and Expenses 2 Spend $80 taking a potential client to lunch and you write off $40. The meal can’t be lavish, and you or an employee must be present. Documentation matters here more than almost anywhere else: for every deductible meal, record the date, the amount, who you ate with, your business relationship, and what you discussed. Vague notes like “business lunch” won’t survive an audit.
The Home Office Deduction
If you use part of your home regularly and exclusively for business, and it serves as your principal place of business or a place where you meet clients, you can deduct a portion of your housing costs. The exclusively requirement is where most claims fall apart. A dining table that doubles as your workspace doesn’t count.
You have two calculation methods. The simplified option gives you $5 per square foot of dedicated business space, up to 300 square feet, for a maximum deduction of $1,500 per year.3Internal Revenue Service. Simplified Option for Home Office Deduction You skip the paperwork of tracking actual costs, but you also forfeit any depreciation deduction on your home.
The actual expense method takes more work but usually produces a bigger deduction. You figure the percentage of your home devoted to business based on square footage, then apply that percentage to mortgage interest, property taxes, utilities, homeowner’s insurance, and repair costs. If your office occupies 15% of the house, you deduct 15% of those expenses. This method requires careful records and a depreciation calculation on the business portion of the home.
Vehicle Expenses
When you drive for business, you pick between two methods. Once you start using the actual expense method for a particular vehicle, you generally can’t switch back to the standard mileage rate for that vehicle.
The standard mileage rate for 2026 is 72.5 cents per mile.4Internal Revenue Service. IRS Sets 2026 Business Standard Mileage Rate at 72.5 Cents Per Mile You multiply that rate by every business mile driven during the year. The only record-keeping is a mileage log showing the date, destination, business purpose, and miles for each trip.
The actual expense method lets you deduct the business percentage of every vehicle operating cost: gas, oil changes, repairs, tires, insurance, registration, and depreciation or lease payments. If 60% of your miles were for business, you deduct 60% of those costs. You need to track both total miles and business miles along with receipts. This method tends to produce a larger deduction for expensive vehicles with high operating costs; the standard mileage rate often wins for cheaper, fuel-efficient cars.
Equipment, Depreciation, and Section 179
When you buy equipment, furniture, a computer, or another asset that will last more than a year, you generally can’t deduct the full cost in the year of purchase. Instead, you spread the cost over the asset’s useful life through depreciation, typically using the Modified Accelerated Cost Recovery System (MACRS) and reporting it on Form 4562.5Internal Revenue Service. About Form 4562, Depreciation and Amortization A computer, for example, has its cost spread across five tax years.
Two provisions let you speed that up. Section 179 allows you to immediately expense the full cost of qualifying assets in the year you place them in service. For 2025, the maximum Section 179 deduction is $2,500,000, with a phase-out starting at $4,000,000 in total equipment purchases.6Internal Revenue Service. Instructions for Form 4562 These limits adjust for inflation each year, and the 2026 limits are expected to be modestly higher. For a sole proprietor buying a vehicle, machinery, or office equipment, Section 179 lets you take the entire deduction up front instead of waiting years.
Bonus depreciation is a separate provision that also allows immediate expensing but has been phasing down. For assets placed in service during 2026, bonus depreciation covers only 20% of the cost, and the rest is depreciated normally under MACRS. For most sole proprietors, Section 179 is the more practical tool because it still provides full first-year expensing within its limits.
Startup and Organizational Costs
If you launched recently, the costs you incurred before opening day get different treatment than ongoing expenses. Market research, advertising for the grand opening, employee training, and travel to scope out suppliers all count as startup costs. You can immediately deduct up to $5,000 of those costs in your first year, but the $5,000 allowance shrinks dollar for dollar once total startup costs exceed $50,000 and disappears entirely at $55,000.7eCFR. 26 CFR 1.195-1 – Election to Amortize Start-Up Expenditures Anything you can’t deduct immediately gets spread over 180 months, starting with the month you open for business.
Organizational costs (legal fees for setting up the business structure, state filing fees, launch-related accounting services) follow the same rules: up to $5,000 immediately deductible with the same $50,000 phase-out, and the remainder amortized over 180 months.7eCFR. 26 CFR 1.195-1 – Election to Amortize Start-Up Expenditures The two categories are tracked separately, so you could deduct up to $10,000 total in year one if costs in each category stay under $50,000.
Self-Employed Health Insurance
Health insurance premiums get special treatment. Rather than appearing as a business expense on Schedule C, they’re claimed as an adjustment to income on your personal return using Form 7206. The practical effect is the same (lower taxable income), but the deduction can’t exceed your net profit from the business. There’s also a catch that trips up many sole proprietors: you can’t claim the deduction for any month you were eligible to participate in a subsidized health plan through your spouse’s employer, even if you chose not to enroll.8Internal Revenue Service. Instructions for Form 7206 The IRS applies this rule month by month, so if your spouse started a new job with benefits in July, you’d lose the deduction only for July through December.
The 20% Qualified Business Income Deduction
On top of every business expense deduction on Schedule C, sole proprietors may qualify for an additional 20% deduction on their qualified business income under Section 199A.9Office of the Law Revision Counsel. 26 USC 199A – Qualified Business Income The QBI deduction doesn’t appear on Schedule C. It’s taken on your personal return and reduces your taxable income, though not your self-employment tax. If your Schedule C shows $100,000 in net profit, QBI could shelter up to $20,000 from income tax.
The math stays simple as long as your total taxable income stays below roughly $200,000 (single) or $400,000 (married filing jointly) for 2026. Above those thresholds, the deduction phases out for certain service-based businesses like law, accounting, health care, and consulting. Below them, you generally get the full 20% regardless of industry. The deduction is available whether you take the standard deduction or itemize, and it was made permanent in 2025 legislation.
Why Every Deduction Is Worth More Than Your Tax Bracket Suggests
Your Schedule C deductions do double duty. They reduce not just your income tax but also your self-employment tax, which funds Social Security and Medicare. The self-employment tax rate is 15.3%: 12.4% for Social Security and 2.9% for Medicare.10Internal Revenue Service. Self-Employment Tax (Social Security and Medicare Taxes) That rate applies to 92.35% of your net profit, not the full amount.11Internal Revenue Service. Understanding Taxes – Module 14 Self-Employment Income and Self-Employment Tax
A sole proprietor earning $80,000 in net profit who finds another $5,000 in legitimate deductions saves not just income tax on that $5,000 but also roughly $707 in self-employment tax (15.3% × 92.35% × $5,000). Combined savings often reach 30% or more of the deduction for someone in the 22% income tax bracket. That’s why chasing down every legitimate expense pays off more for a self-employed person than for an employee looking at itemized deductions.
Records the IRS Will Actually Accept
The burden of proving every deduction falls entirely on you. The IRS can disallow any expense you can’t substantiate with records showing the amount, date, business purpose, and, for meals, who was involved and what was discussed. Receipts, invoices, bank statements, and credit card records all count as evidence.
Vehicle and travel deductions require a contemporaneous log. For mileage, that means recording the odometer at the start and end of each year plus the date, destination, business purpose, and miles for each trip. Reconstructing a mileage log after the fact is one of the fastest ways to lose a deduction in an audit.
Keeping business finances separate from personal finances is the single most effective thing you can do. A dedicated business bank account and credit card create a clean audit trail and make it obvious which expenses were business-related. Commingling funds makes bookkeeping harder and gives an auditor reason to scrutinize every transaction more closely.
Retain your records for at least three years from the date you filed or the return’s due date, whichever is later.12Internal Revenue Service. How Long Should I Keep Records If you underreported income by more than 25%, the IRS has six years to audit. Records for property you’re depreciating should be kept until three years after you dispose of the asset, so the IRS can verify your cost basis.13Internal Revenue Service. Topic No. 305, Recordkeeping
Where the Deductions Actually Go on Your Return
All business income and deductions flow through Schedule C (Profit or Loss From Business), which attaches to your Form 1040.14Internal Revenue Service. About Schedule C (Form 1040), Profit or Loss From Business (Sole Proprietorship) The form runs revenue at the top and categories of expenses in the middle: advertising, insurance, office supplies, utilities, and so on. The bottom line is your net profit or loss, which feeds two places: Form 1040 for income tax and Schedule SE for self-employment tax.
Home office claims use Form 8829 or the simplified method line on Schedule C. Vehicle expenses using the actual method require Part IV of Schedule C for auto information. Depreciation and Section 179 deductions go through Form 4562 before landing on Schedule C. The forms feed each other, so the net profit on Schedule C already reflects every deduction claimed across the supporting forms.