As a sole proprietor, there is no separate business tax return. Your business lives on Schedule C, a form attached to your personal Form 1040. The profit from Schedule C flows into your personal income, and that profit drives two different taxes.
Tax one: income tax on your profit
You pay income tax on your net profit — revenue minus legitimate business expenses — at your ordinary income tax rate. If your business made $60,000 after expenses, that $60,000 stacks on top of any other household income and is taxed at whatever bracket it lands in.
Tax two: self-employment tax
This is the one that shocks first-year owners. When you had a W-2 job, your employer paid half of your Social Security and Medicare taxes. As a sole proprietor you pay both halves — 15.3% on the bulk of your net profit (12.4% for Social Security up to the annual cap, 2.9% for Medicare, with an additional Medicare tax at higher incomes). You do get to deduct the employer-equivalent half when calculating your income tax, which softens it slightly.
A rough planning number many preparers use: set aside 25–30% of your net profit for federal taxes until you know your real rate. Your actual percentage depends on your state, your other income, and your deductions.
The four deadlines
Because no employer is withholding taxes for you, the IRS expects payment as you earn — quarterly estimated taxes, generally due April 15, June 15, September 15, and January 15 of the following year. Miss them and you can owe an underpayment penalty even if you pay in full in April. If your income is uneven, your preparer can use the annualized income method so the payments match when you actually earned the money.
The deduction that does double duty
Every legitimate business expense reduces both taxes at once — it lowers the profit that income tax applies to and the profit that self-employment tax applies to. That is why expense tracking is not clerical work; it is the single biggest lever you control. A sole proprietor who misses $8,000 of legitimate expenses does not just overpay income tax — they overpay self-employment tax on the same $8,000.
Most sole proprietors can also deduct a portion of their qualified business income — the qualified business income deduction — on their personal return. The rules have income limits and exceptions, so confirm your eligibility with a tax professional.
Where sole proprietors get hurt
Not the tax rates — the records. Cash and app payments that never got logged, expenses reconstructed from memory in March, a mileage number invented at the kitchen table. Every gap in the record is either income you cannot prove or a deduction you cannot take. The businesses that pay the least tax legally are not smarter. They just wrote everything down.
LedgerFast keeps the record complete all year — cash and app income logged in seconds, expenses mapped to Schedule C categories as they happen, and a Tax Organizer ready for your preparer in January. Plans from $49/month, first month free.
Disclaimer
This article is general educational information, not tax, legal, or accounting advice. LedgerFast is not a CPA firm and does not provide tax preparation or filing services. Tax rates, caps, and deadlines change and depend on your circumstances — consult a qualified tax professional. Use of LedgerFast is governed by our Terms of Service.