When Are Quarterly Estimated Tax Payments Due?

Quarterly estimated tax payments are due on four fixed dates each year: April 15, June 15, September 15, and January 15 of the following year. These dates cover unequal periods of income, not clean three-month quarters, and each one applies to any taxpayer, individual, sole proprietor, partner, or S-corp shareholder, who expects to owe $1,000 or more in tax after subtracting withholding and refundable credits. If a date falls on a Saturday, Sunday, or legal holiday, the deadline moves to the next business day.

What are the four estimated tax due dates for 2026?

The four 2026 due dates are April 15, 2026; June 15, 2026; September 15, 2026; and January 15, 2027. Each one corresponds to a specific income period rather than a calendar quarter:

None of the 2026 due dates land on a weekend or federal holiday, so no payment shifts to a later business day this cycle. April 15, 2026 is a Wednesday, June 15 is a Monday, September 15 is a Tuesday, and January 15, 2027 is a Friday. Don't assume that holds every year; it won't.

Why does the fourth "quarter" only cover four months?

The fourth payment period runs September 1 through December 31, four months instead of three, because the IRS collapses the last two calendar quarters into a single January 15 due date. It's not a glitch in the software or a typo somewhere upstream. Congress wrote the four payment periods into the tax code as unequal spans, and the IRS has run the schedule that way for decades. If a client asks why Q4 feels short-changed, that's the answer: there is no Q4 payment in the sense a calendar quarter would suggest, just a January catch-up date that happens to close out a longer stretch of income.

What happens if a due date falls on a weekend or holiday?

If a due date falls on a Saturday, Sunday, or IRS-recognized legal holiday, including a state holiday that closes the local IRS office, the payment is on time as long as it's made by the next business day. This is the same rule that governs the April filing deadline, and it applies independently to each of the four estimated tax dates. It doesn't apply uniformly across years, though. A Monday holiday following a weekend deadline can push a date out by two business days instead of one, and Emancipation Day (observed in D.C. on April 16 some years) has shifted the April deadline before. Check the specific year's calendar each January rather than assuming last year's shift pattern repeats. A firm that hardcodes "the 15th, or the following Monday if it's a weekend" into a spreadsheet formula will eventually get a date wrong.

How does a firm actually track this across a client list?

Once you're past a handful of clients, tracking estimated payment dates by memory or a shared calendar breaks down fast. A 150-client 1040 book has a mix of quarterly filers, some with wildly different income patterns quarter to quarter, so a static reminder four times a year isn't enough. What holds up in practice:

• Flag estimated-payment status at the point of prior-year return prep, not four months later when Q1 is already due.

• Track voucher amounts against actual year-to-date income for clients with volatile earnings (real estate agents, contractors, anyone with a bonus-heavy comp structure), so the Q3 or Q4 voucher isn't just last year's number divided by four.

• Confirm state estimated payment dates separately. Several states don't mirror the federal schedule exactly, and a preparer who assumes they do will miss a state deadline while hitting the federal one.

• Build the reminder around the payment date, not the return-prep date. A client who paid Q1 on time in April can still miss Q3 in September if nobody flagged it.

This is the kind of repetitive, date-driven tracking that's easy to get right in January and easy to let slip by September, which is exactly why it's worth automating rather than running off memory or a static calendar reminder.

Do I still need to pay the January 15 installment if I'll file my return early?

No. A taxpayer who files their full return and pays any remaining balance by January 31 of the following year isn't required to make the separate January 15 estimated payment for that tax year. The exception exists so someone who has already finished their return doesn't also need to cut an estimated payment check weeks before filing anyway. It does not extend to the April, June, or September due dates, and it only works if the return is actually filed and paid in full by January 31, not just started.

Who actually has to make these payments?

Anyone who expects to owe at least $1,000 in tax for the year, after withholding and refundable credits, generally has to make estimated payments on this schedule. That catches most self-employed taxpayers, partners receiving Schedule K-1 income, and S-corp shareholders taking distributions, since none of them have an employer withholding tax throughout the year. W-2 employees with significant outside income (rental, investment, or side-business income) can also land in this bucket even with some withholding coming out of a paycheck.

Whether a specific client is required to pay, and how much, comes down to the safe-harbor rules: paying in at least 90% of the current year's tax or 100% of last year's tax (110% if last year's AGI was over $150,000) avoids the underpayment penalty regardless of what's actually owed at filing. A client who's on track to owe more this year than last can often get by paying only the safe-harbor amount quarterly and settling the rest in April. That calculation is where a lot of the real prep work sits, not just knowing the four dates but running the safe-harbor numbers correctly for a client whose income shifted year over year.

Missing one of these four dates, or underpaying against them, is what triggers the separate underpayment penalty calculation. That penalty runs on the current federal short-term rate plus 3%, compounded, for the exact number of days each installment was late. A client who skips Q1 and Q2 and tries to true up everything in Q3 still owes penalty interest on the earlier shortfall, even after the later payment is made in full.

SignalsHQ helps CPA firms track estimated-payment due dates and safe-harbor calculations automatically as part of the return workflow, see how it fits your firm's 1040 process.