A quarterly estimated payment is one quarter of the tax you expect to owe for the year, minus any withholding already covered. You estimate the full year's tax — self-employment tax plus income tax — subtract what a W-2 job is already withholding, and divide the rest by four. For 2026 the payments are due April 15, June 15, and September 15 of 2026, and January 15 of 2027. The Quarterly Estimated Tax Calculator runs the whole sequence; this guide explains each piece of it.
Why the IRS collects tax four times a year
The US income tax is pay-as-you-go. Employees barely notice: their employer withholds a slice of every paycheck and sends it to the IRS continuously through the year. The IRS expects the same rhythm from the self-employed — it simply cannot withhold from you, so it asks you to send the money yourself, in four installments, as the income arrives.
Two problems follow when the rhythm is skipped. The formal one is an underpayment penalty, charged like interest on each quarter's shortfall. The practical one is worse for most freelancers: a full year of tax landing in a single April, months after the money that should have paid it was spent. Quarterly payments are less a tax rule than a cash-flow system — four small, dated bills instead of one large surprise.
The four 2026 due dates
- April 15, 2026 — for income earned January through March
- June 15, 2026 — for income earned April through May
- September 15, 2026 — for income earned June through August
- January 15, 2027 — for income earned September through December
Notice the uneven spacing: the second deadline arrives only two months after the first, because the IRS periods cover three, two, three, and four months of income respectively. The payments, however, are usually equal — the standard schedule divides the year's expected tax by four regardless of the uneven periods, which is the schedule this guide and the linked tools use.
How a quarterly amount is built
Three steps, in order. First, estimate the year's total tax. For a freelancer that means self-employment tax — 15.3% on 92.35% of net profit, with the Social Security part capped at the 2026 wage base of $184,500 — plus federal income tax on what remains after the half-of-SE-tax deduction and the standard deduction, plus state tax where your state has one. The Self-Employment Tax Estimator shows that total broken into its components, and the Tax Bracket Calculator shows which brackets the income-tax part passes through.
Second, subtract withholding and payments already made. W-2 withholding — yours from a part-time job, or a spouse's on a joint return — counts toward the same obligation, dollar for dollar, and the IRS treats it as paid evenly across the year even when it happens late in the year. Third, divide what remains by four. Rounding is handled the way Form 1040-ES handles it: the first three payments are the rounded quarter amount and the final payment takes the remainder, so the four always add up to the exact balance.
Worked example — $95,000 of net profit, split four ways
Daniel is a single freelance consultant in Texas expecting $95,000 of net self-employment income in 2026. A part-time W-2 job will withhold $2,000 toward the same obligation. (Assumptions: single filer, 2026 figures throughout, no state income tax in Texas, and no QBI deduction, credits, or other adjustments — the same exclusions the linked estimator states.)
- Adjusted SE base: $95,000 × 92.35% = $87,732.50
- Social Security: $87,732.50 × 12.4% = $10,878.83 (the base is under the $184,500 wage base)
- Medicare: $87,732.50 × 2.9% = $2,544.24
- Self-employment tax: $13,423.07
- Adjusted gross income: $95,000 − $6,711.54 (half of SE tax) = $88,288.46
- Taxable income: $88,288.46 − $16,100 (2026 single standard deduction) = $72,188.46
- Federal income tax: 10% × $12,400 ($1,240.00) + 12% × $38,000 ($4,560.00) + 22% × $21,788.46 ($4,793.46) = $10,593.46
- Total estimated 2026 tax: $13,423.07 + $10,593.46 = $24,016.53 — an effective rate of about 25.3% of net profit
- Less W-2 withholding already covered: −$2,000.00 → remaining to pay through estimates: $22,016.53
- Quarterly payments: $5,504.13, $5,504.13, $5,504.13, and a final $5,504.14 (the last payment absorbs the rounding remainder) — due April 15, June 15, and September 15, 2026, and January 15, 2027
Two things to notice. The $2,000 of withholding quietly removed $500 from every quarterly check — withholding is the easiest estimated payment there is, because it happens before the money reaches you. And the effective rate, about 25.3%, is why the common advice to set aside 25–30% of every invoice exists: on these figures it is almost exactly right.
The safe harbor: the target that actually protects you
You do not have to forecast your income perfectly to avoid the underpayment penalty — you have to clear a lower, knowable bar. The IRS generally waives the penalty if your payments for the year reach either 90% of the tax you actually owe for 2026, or 100% of last year's total tax — that second figure rises to 110% if your prior-year adjusted gross income was over $150,000.
That makes last year's return a strategy, not just a record. If last year's tax is the smaller number and your income is jumping this year, basing payments on it shelters you completely; you settle the difference the following April, penalty-free. If your income fell, the 90%-of-actual route is the cheaper target, and it is the one an estimate like the worked example above is built to hit. Either way, aim at one of the two targets deliberately instead of guessing a round number.
When your income is uneven
Equal installments assume income arrives evenly, and freelance income rarely does. If most of your money lands late in the year, equal early payments overpay early and strain cash flow; if it lands early, they can underpay the early periods. The IRS answer is the annualized income installment method (Form 2210, Schedule AI), which sizes each payment from the income actually earned by that point in the year. It costs some paperwork at filing time and can erase penalties the ÷4 schedule would have triggered for seasonal earners. The equal-installment figure is still the right starting point — it is the baseline the annualized method is compared against.
Estimates only — not tax advice. This guide explains the standard estimated-tax method for educational and planning purposes, using 2026 IRS figures (92.35% adjustment, $184,500 Social Security wage base, 2026 brackets and standard deduction). It is not professional tax advice: it excludes the qualified business income deduction, credits, and state-specific rules, any of which can change your real liability. Verify your deadlines, safe harbor amounts, and payment figures at irs.gov or with a qualified tax professional before paying.