If nobody withholds tax from your income, the IRS expects you to send it yourself four times a year. Here is the whole system in one page.
Who pays
Anyone who expects to owe $1,000 or more in federal tax after withholding. Freelancers, contractors, gig workers, landlords with significant income, S corp owners whose salary withholding does not cover distributions.
2026 due dates
- April 15, 2026 (Q1)
- June 15, 2026 (Q2)
- September 15, 2026 (Q3)
- January 15, 2027 (Q4)
How much
Either estimate this year's tax and pay a quarter each time, or use the safe harbor: pay 100% of last year's total tax (110% if AGI was over $150,000) in four equal installments and no penalty applies regardless of what you owe in April. The calculator does both.
How to pay
IRS Direct Pay at irs.gov/payments, or through your IRS Online Account. Choose 'Estimated tax' and the tax year. Save the confirmation. Most states have an equivalent.
Uneven income
If most of your income lands in one quarter, you can pay based on actual profit each period (Form 2210 Schedule AI). This only works if your books are current, which is the real argument for monthly bookkeeping.