How quarterly estimated taxes work
When you have a W-2 job, your employer withholds federal income tax and FICA from every paycheck and sends it to the IRS on your behalf. When you're self-employed, nobody does that for you. The IRS wants its money on a roughly quarterly schedule anyway, so it built a system called "estimated taxes" that freelancers, contractors, landlords, and anyone with meaningful untaxed income has to use. You project how much you'll owe for the year, divide by four, and send a check (or ACH payment) four times a year using Form 1040-ES.
The four 2026 quarterly deadlines are not evenly spaced, which confuses people every year. They are: April 15, 2026 (covers income earned Jan 1 to Mar 31), June 16, 2026 (covers April 1 to May 31), September 15, 2026 (covers June 1 to Aug 31), and January 15, 2027 (covers Sept 1 to Dec 31). Notice Q2 is only two months long and Q4 is four months long — that's how the IRS drew the lines, don't overthink it.
What counts toward "estimated tax"
Your quarterly estimated tax payment needs to cover three things: federal income tax on your business income, self-employment tax (Social Security + Medicare on your net earnings), and any additional Medicare surtax if you cross the threshold. It does not cover state income tax — that's a separate schedule handled by your state's tax department, and most states with income tax have their own 1040-ES equivalent you need to file too.
This calculator handles the federal piece. If you live in California, New York, Massachusetts, or another high-tax state, you'll want to tack on another 5 to 10 percent of your taxable income as a state estimated payment and send it separately to your state.
The safe harbor rule that keeps you out of penalties
The IRS charges an underpayment penalty if you pay too little in estimated taxes. But there's a "safe harbor" that protects you even if your actual tax bill ends up much bigger than you projected. The safe harbor says you can avoid the penalty by paying the smaller of: (1) 90 percent of your current year's total tax, or (2) 100 percent of last year's total tax — bumped to 110 percent if your prior year AGI was over $150,000.
For most freelancers, path #2 is the easier guarantee. Look at your prior year's Form 1040 line 24 (total tax). Divide it by four. Pay that amount each quarter. You are bulletproof against penalties regardless of how much you end up earning. If your income grows, you might owe more at year end, but you won't get hit with an IRS underpayment penalty.
A worked example
Say you're a single freelancer expecting $70,000 of net self-employment income in 2026, no W-2 wages, no other income. Plug those numbers in above and you'll see: projected total federal tax around $16,600, split into four payments of roughly $4,150 each due April 15, June 16, September 15, and January 15. That's what you send the IRS via Form 1040-ES (electronically at EFTPS.gov or IRS Direct Pay, or by mailing a paper voucher).
Common mistakes that trip up freelancers
Mistake one: forgetting that SE tax alone is 15.3 percent on top of your income tax. People remember their bracket and forget the self-employment portion. Mistake two: treating the estimated payment as optional. The IRS considers underpayment penalties a cost of doing business and will assess them. Mistake three: paying based on gross revenue instead of net (post-expense) income. You only owe tax on profit, not on top-line sales. Mistake four: forgetting state. If you live somewhere with income tax, you owe estimated payments there too, on roughly the same schedule.
How to actually send the payment
Two recommended methods: (1) Use IRS Direct Pay at directpay.irs.gov — free, ACH from your bank, no account needed, takes about three minutes. (2) Use EFTPS.gov — slightly more setup, but lets you schedule all four payments at the start of the year so you can't forget. Both are free and give you a confirmation number.
Avoid credit card payments unless you really need to — the IRS charges a ~1.85% processing fee which typically exceeds any rewards you'd earn. Avoid mailing checks unless you like certified mail receipts and tracking. The electronic methods are faster and generate automatic records.