Sole proprietorship accounting works on one principle: the IRS treats you and your business as the same taxpayer, so there is one set of books, one tax return, and one person responsible for the result. Every dollar of profit and every deductible expense flows onto your personal Form 1040 through Schedule C. Understanding that single idea makes every other decision — how to keep records, when to recognize income, what to deduct, how much to pay in quarterly tax — fall into place.
One Taxpayer, One Set of Books
You become a sole proprietor the moment you start earning business income without forming a corporation, LLC, or partnership. No paperwork creates the structure. The IRS calls it a “disregarded entity,” meaning the business itself does not file a return. Your financial statements are internal tools for calculating net profit; they are not filed with the IRS the way a corporation’s are.
The practical consequence for your books is simple. You keep records good enough to prove your income and expenses to the IRS, and you use those records to fill out Schedule C once a year. You do not file a separate business return. You do not issue yourself a W-2. Your “paycheck” is the profit itself, and it is taxed whether you withdraw it or leave it sitting in the business account.
The disregarded-entity label has a less comfortable consequence outside the books: unlimited personal liability. Every business debt is your debt, and creditors can reach your personal assets. That risk is one of the main reasons sole proprietors eventually form an LLC or corporation, but it does not change how the accounting works while you remain a proprietor.
Separate the Money, Even When the Law Doesn’t
The law may see no boundary between you and your business, but your books should. Mixing personal and business transactions in one account creates a tangle at tax time, weakens your position in an audit, and tends to cost you deductions you forgot to claim.
The IRS requires records that clearly show your income and expenses.1Internal Revenue Service. What Kind of Records Should I Keep For most small businesses, the checking account is the main source of entries. Open a dedicated business checking account, run every dollar of business income and expense through it, and keep personal spending out. Save receipts, keep copies of invoices you send, and hold onto bank and credit card statements. A spreadsheet that tracks income and expenses by category is enough to start; accounting software becomes worthwhile once transaction volume justifies the automation.
Choosing Cash or Accrual Accounting
Your accounting method decides when income and expenses hit the books. You lock in the choice on your first Schedule C, and switching later requires IRS approval.2Internal Revenue Service. Publication 334 – Tax Guide for Small Business
Most sole proprietors use the cash method because it mirrors the bank account. Income counts when the money arrives; expenses count when you pay them. Send an invoice in December that gets paid in January, and the income belongs to next year. The method also gives you some control over taxable income by letting you time when bills get paid.
The accrual method counts income when you earn it and expenses when you incur them, regardless of when cash moves. It paints a more accurate picture of profitability at any given moment, but it is more work to maintain and can leave you paying tax on money you have not yet collected.
Inventory used to force the accrual method, but a small business taxpayer exception now covers most sole proprietors. You qualify as long as your average annual gross receipts over the prior three years stay below an inflation-adjusted threshold, currently in the range of $30 to $31 million.3Office of the Law Revision Counsel. 26 U.S. Code 448 – Limitation on Use of Cash Method of Accounting Virtually all sole proprietors sit well below that line.
Owner’s Capital and Owner’s Draws
You do not pay yourself a salary. Two equity accounts handle the money flowing between you and the business.
Owner’s capital tracks your total investment. It goes up when you contribute personal money or assets and when the business earns net income. It goes down with net losses. Think of it as a running measure of how much value you have tied up in the business.
Owner’s draws track money you take out for personal use. Draws are not business expenses and do not reduce your taxable income. They reduce your equity, nothing more. Whether you withdraw $5,000 for the year or leave every dollar in the account, the full net profit is taxed the same way. The draw account exists so you can see what you have pulled out.
Deductions That Reduce Your Tax Bill
Every legitimate business expense you track lowers your taxable profit. The IRS requires a deductible expense to be both “ordinary” (common in your industry) and “necessary” (helpful and appropriate), and necessary does not mean indispensable.4Internal Revenue Service. Ordinary and Necessary Beyond the obvious — supplies, advertising, professional services — a handful of deductions do most of the heavy lifting for sole proprietors.
Home Office
If you use part of your home regularly and exclusively for business, you can deduct a share of your housing costs. The simplified method pays $5 per square foot of dedicated workspace, capped at 300 square feet and $1,500.5Internal Revenue Service. Simplified Option for Home Office Deduction The regular method applies the business-use percentage of your home against real expenses like rent, utilities, and insurance. More recordkeeping, usually a bigger deduction.
Business Mileage
When you use a personal vehicle for business, you can deduct either actual vehicle expenses or the standard mileage rate. For 2026, the IRS rate is 72.5 cents per mile.6Internal Revenue Service. IRS Sets 2026 Business Standard Mileage Rate at 72.5 Cents Per Mile, Up 2.5 Cents Keep a mileage log with the date, destination, business purpose, and miles. Without one, the deduction is nearly impossible to defend.
Self-Employed Health Insurance
Sole proprietors who buy their own coverage can deduct 100% of premiums paid for themselves, a spouse, and dependents. The deduction is claimed on Schedule 1 as an adjustment to gross income, not on Schedule C, so you get it whether you itemize or take the standard deduction.7Internal Revenue Service. Instructions for Form 7206 You must show a net profit on Schedule C, and you cannot claim the deduction for any month you were eligible for an employer-sponsored plan through your own job or a spouse’s.
Retirement Contributions
A SEP IRA lets you contribute up to 25% of net self-employment earnings, with a 2026 maximum of $72,000.8Internal Revenue Service. SEP Contribution Limits (Including Grandfathered SARSEPs) Contributions reduce adjusted gross income. A Solo 401(k) can allow higher contributions at lower income levels because it includes both an employee and employer component.
Qualified Business Income
Sole proprietors may qualify for a deduction of up to 20% of qualified business income under Section 199A. Below taxable income of roughly $201,750 (or about $403,500 for married couples filing jointly), the full 20% generally applies with no additional restrictions. Above those thresholds the deduction begins to phase out, and service businesses like consulting, law, and accounting face stricter limits. The deduction is taken on your personal return, not on Schedule C.
Filing Schedule C and Schedule SE
Schedule C turns a year of bookkeeping into a tax document. It starts with gross receipts, subtracts cost of goods sold if applicable, lists deductible business expenses by category, and arrives at net profit or loss. That number flows to your Form 1040.9Internal Revenue Service. About Schedule C (Form 1040) – Profit or Loss From Business
You file Schedule C regardless of how much you earned. The familiar $400 figure is the threshold for self-employment tax, not for Schedule C itself. When net self-employment earnings reach $400 or more, you also file Schedule SE.10Internal Revenue Service. Schedule C and Schedule SE Below $400, the income still goes on Schedule C and the 1040.
Self-Employment Tax
You pay both the employer and employee shares of Social Security and Medicare. The combined rate is 15.3%: 12.4% for Social Security plus 2.9% for Medicare.11Internal Revenue Service. Self-Employment Tax – Social Security and Medicare Taxes Before the rate is applied, you multiply net earnings by 92.35% to reach the taxable base, which effectively mirrors the employer-side treatment traditional employees receive.
The 12.4% Social Security portion applies only to net earnings up to $184,500 in 2026.12Social Security Administration. Contribution and Benefit Base Earnings above that cap drop out of the Social Security piece. The 2.9% Medicare portion has no cap. When combined wages and self-employment income exceed $200,000 ($250,000 for married filing jointly), an additional 0.9% Medicare tax applies to the amount above the threshold.13Internal Revenue Service. Questions and Answers for the Additional Medicare Tax
You can deduct half of your self-employment tax when calculating adjusted gross income. The deduction appears on Schedule 1 and reduces income tax, but it does not reduce the self-employment tax itself.
Quarterly Estimated Payments
Nobody withholds tax from your business profit, so you pay as you go. For 2026, the quarterly due dates are April 15, June 15, September 15, and January 15, 2027.14Internal Revenue Service. 2026 Form 1040-ES File your 2026 return and pay the full balance by February 1, 2027, and you can skip the January payment.
Underpaying triggers a penalty calculated on each underpayment for the days it remains unpaid. You avoid the penalty by meeting any one of three safe harbors:
- Your total tax due after withholding and refundable credits comes in under $1,000 when you file.
- You paid at least 90% of the tax shown on your 2026 return through estimated payments and withholding.
- You paid at least 100% of the tax shown on your 2025 return. If 2025 adjusted gross income exceeded $150,000 ($75,000 if married filing separately), the threshold rises to 110%.
The prior-year safe harbor is the easiest to use because the number is already known. Many sole proprietors divide last year’s total tax by four and pay that each quarter, adjusting only if income shifts sharply.15Internal Revenue Service. Underpayment of Estimated Tax by Individuals Penalty
Do You Need an EIN?
Most sole proprietors can file using their Social Security Number. You need a separate Employer Identification Number if you hire employees, file excise tax returns, or contribute to a Keogh retirement plan. An EIN is free directly from the IRS, and one is enough regardless of how many trade names you operate under.16Internal Revenue Service. Instructions for Form SS-4 If the business later incorporates or becomes a partnership, a new EIN is required.