The US tax system runs on pay-as-you-go. W-2 employees do this automatically through paycheck withholding. Freelancers, contractors, and self-employed business owners do it manually through four estimated payments per year. The mechanics sound bureaucratic but the rules are actually simple, and getting them right protects you from the underpayment penalty that quietly stings a lot of new freelancers.
When quarterly payments are due
The four 2026 due dates are April 15 (January-March income), June 16 (April-May), September 15 (June-August), and January 15, 2027 (September-December). Q2 is June 16 because June 15 falls on a Sunday. Notice the quarters are not equal - the second period is two months and the fourth is four. This is just how the IRS schedules it.
The two safe-harbor rules
The IRS will not assess an underpayment penalty if you meet either of two safe harbors. **Rule 1: 90% of current year.** Pay at least 90% of this year's actual total tax through quarterly payments and withholding. **Rule 2: 100% of prior year (110% if AGI > $150k).** Pay at least 100% (or 110% for high earners) of last year's total tax in equal installments. Most freelancers use Rule 2 because it is fixed in advance and immune to mid-year income surprises — you literally cannot under-pay.
How to calculate each quarter
For the safe-harbor approach, take last year's total tax (line 24 on Form 1040), apply the 110% multiplier if applicable, and divide by four. That number is your quarterly payment, due on each of the four dates above. For the current-year approach, project this year's total income, run it through the 1099 Tax Calculator to get an estimated annual tax, and divide by the number of remaining quarters.
Who actually has to pay quarterly
You owe estimated payments if you expect to owe at least $1,000 in tax for the year after withholding and credits. Almost every full-time freelancer crosses that threshold. Side-hustlers with a primary W-2 job may be able to skip quarterly payments if they bump up W-2 withholding enough to cover the side-income tax — a useful trick because withholding is treated as paid evenly throughout the year regardless of when it actually happens.
What happens if you miss a payment
The underpayment penalty is calculated as interest on the shortfall, computed for each quarter you were short. It is not a fixed dollar amount — for typical freelance underpayments it works out to a few percent annually on the missed amount. Not catastrophic, but completely avoidable.
How to actually pay
The IRS Direct Pay system (irs.gov/payments) lets you pay each quarterly estimate from a bank account with no fee. You can also pay by debit/credit card (small processing fee), through EFTPS, or by mailing Form 1040-ES with a check. State estimated payments are separate — most states with income tax have their own portal and quarterly schedule that mirrors the federal one.
Tools and guides
The 1099 Tax Calculator outputs a total annual tax estimate that you can divide by four for safe-harbor planning. The Self-Employment Tax Guide walks through the worksheet most CPAs use. A dedicated Quarterly Estimated Tax Planner is on the roadmap that will split your annual estimate into the four IRS due dates automatically.