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Not financial or tax advice
This guide explains how self-employment tax works and how to build a system around it. Your specific tax situation depends on income level, entity type, state, and other factors. Work with a CPA for your actual numbers — especially around S-Corp election and quarterly estimates.

The tax problem every solo operator faces

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Self-employment tax is 15.3%

You pay both the employee and employer share of Social Security and Medicare. On a W-2 job, your employer covers half. As a solo operator, it's all yours — on top of income tax.

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Four payment deadlines a year

Quarterly estimated taxes are due in April, June, September, and January. Miss them and the IRS charges underpayment penalties — even if you pay in full at tax time.

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No withholding means no safety net

Every payment from every client hits your account pre-tax. Unless you move money to a dedicated tax account immediately, it mixes with operating cash and disappears before April.

The two-part solution

Part 1 — Separation
A dedicated tax account, funded automatically

Open a separate business checking account for taxes only. Set an automatic transfer rule: every time income lands, move 25–30% to the tax account immediately. Use Relay's percentage-based transfer rules to do this without manual action.

Open Relay for Profit First tax allocation →
Part 2 — Visibility
Accounting software that tracks income in real time

You need to know your net profit to calculate what you owe. FreshBooks or QuickBooks — synced to your bank — gives you a running P&L that makes quarterly estimates accurate instead of guesses.

Compare accounting software for solo operators →

2026 quarterly estimated tax deadlines

Quarter Income Period Due Date How to Pay
Q2 Apr 1 – May 31 June 16, 2026 IRS Direct Pay or EFTPS
Q3 Jun 1 – Aug 31 September 15, 2026 IRS Direct Pay or EFTPS
Q4 Sep 1 – Dec 31 January 15, 2027 IRS Direct Pay or EFTPS

Note: Deadlines shift when they fall on weekends or federal holidays. Q2 covers only 2 months (April–May), not 3 — a common source of underpayment. Verify current deadlines at IRS.gov.

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The safe harbor rule — avoid penalties automatically
You avoid IRS underpayment penalties if you pay at least 100% of last year's tax liability in equal quarterly installments (110% if your prior-year AGI exceeded $150K). This is called the "safe harbor" method. If your income is growing, this may mean you still owe at tax time — but you won't owe penalties. Ask your CPA which method makes sense for your situation.