The four estimated tax due dates in 2026 are April 15 (Q1), June 15 (Q2), September 15 (Q3), and January 15, 2027 (Q4). These deadlines apply to self-employed individuals, sole proprietors, partners, S-corp shareholders, and C corporations whose tax withholding will fall short of their full liability. Missing any one of them triggers an underpayment penalty even if you are due a refund at year-end, per the IRS estimated tax FAQ (last reviewed December 2025).
TL;DR
- The 2026 quarterly deadlines are April 15, June 15, September 15, and January 15, 2027 — mark all four now because the periods are uneven in length.
- You avoid the underpayment penalty by paying at least 90% of your 2026 liability or 100% (110% if AGI > $150,000) of your 2025 tax — whichever is smaller.
- C corporations follow the same quarterly dates but use Form 1120-W; S-corp and partnership owners pay individually on Form 1040-ES.
What are the estimated tax due dates 2026 for each quarter?
Each of the four payment periods has its own due date set by the IRS, and the periods are not equal in length. The first period spans three months, the second only two, the third three, and the fourth four. That asymmetry catches people off guard every year — particularly clients who receive a large capital gain in May and assume the next payment window is far away.
| Payment | Income Period Covered | Due Date | Form |
|---|---|---|---|
| Q1 2026 | January 1 – March 31 | April 15, 2026 | Form 1040-ES |
| Q2 2026 | April 1 – May 31 | June 15, 2026 | Form 1040-ES |
| Q3 2026 | June 1 – August 31 | September 15, 2026 | Form 1040-ES |
| Q4 2026 | September 1 – December 31 | January 15, 2027 | Form 1040-ES |
If a due date falls on a Saturday, Sunday, or federal holiday, the IRS moves the deadline to the next business day. All four 2026 dates above land on weekdays, so no shifts apply this cycle. Payments can be made online through IRS Direct Pay, by phone, through EFTPS, or via the IRS2Go mobile app.
How do C corporation estimated tax dates differ from individual dates?
C corporations follow the same four calendar due dates as individuals — April 15, June 15, September 15, and January 15, 2027 — but they use Form 1120-W to calculate each installment and the payment threshold is lower. A C corporation must make estimated payments when it expects to owe $500 or more for the year, compared to the $1,000 threshold for individuals.
S corporations themselves generally do not pay income tax at the entity level; the tax obligation passes through to each shareholder's personal return. However, an S corporation can owe estimated taxes on certain built-in gains, excess net passive income, or investment credit recapture if those totals reach $500 or more, per the IRS.
Who is required to make estimated tax payments in 2026?
You are generally required to make 2026 estimated payments if both of the following are true: you expect to owe at least $1,000 in federal tax after subtracting withholding and refundable credits, and your withholding plus refundable credits will cover less than the smaller of 90% of your 2026 tax or 100% of your 2025 tax (110% if your 2025 adjusted gross income exceeded $150,000, or $75,000 if married filing separately).
This applies to sole proprietors, freelancers, partners, S-corp shareholders, rental property owners, and anyone with investment income not covered by withholding. W-2 employees whose side income pushes their underpayment above $1,000 are also on the hook. The IRS's Publication 505, Tax Withholding and Estimated Tax, covers every edge case including farming and fishing income rules.
What is the safe harbor rule and how do you calculate each payment?
The safe harbor rule is the fastest way to confirm your clients won't owe a penalty: if total payments equal at least 100% of last year's tax (or 110% for higher-income taxpayers), the underpayment penalty does not apply regardless of the actual 2026 liability. This is often the most practical approach when 2026 income is hard to predict early in the year.
The two main calculation methods are:
- Prior-year safe harbor: Divide the total tax from the 2025 return by four and pay that amount each quarter. Simple and penalty-proof.
- Current-year estimate: Project 2026 income and compute 90% of the expected liability, then divide by four. More accurate but requires updated income estimates before each deadline.
When income is highly uneven — a client who closes a business sale in Q3, for example — the annualized income installment method on Form 2210 Schedule AI lets you match payments to the period the income actually arrived. It takes more time to calculate but can eliminate a penalty that would otherwise stack up on the earlier quarters.
What is the full 2026 tax deadline calendar beyond estimated payments?
Estimated payments sit inside a wider calendar of filing deadlines your firm tracks each year. The table below shows the complete picture for calendar-year filers, sourced from the MCB CPA 2026 deadline calendar.
| Date | Obligation |
|---|---|
| January 15, 2026 | Q4 2025 individual estimated tax payment due |
| February 2, 2026 | W-2s to employees; 1099-NEC / 1099-MISC to recipients and IRS |
| March 16, 2026 | Form 1065 (partnerships) and Form 1120-S (S-corps) due |
| April 15, 2026 | Form 1040 (individuals), Form 1120 (C-corps), Form 1041 (trusts); Q1 2026 estimated payment due; IRA / HSA contribution deadline for 2025 |
| June 15, 2026 | Q2 2026 estimated payment due |
| July 31, 2026 | Form 5500 (employee benefit plans) |
| September 15, 2026 | Q3 2026 estimated payment due; extended Form 1065 and Form 1120-S due |
| September 30, 2026 | Extended Form 1041 (trusts) due |
| October 15, 2026 | Extended Form 1040 and Form 1120 due |
| January 15, 2027 | Q4 2026 estimated payment due (individuals and C-corps) |
Notice that September 15 is doing double duty: it is both the Q3 estimated payment date and the extended deadline for partnership and S-corp returns. Clients who are also partners in another entity may have two obligations land on the same day, so flagging that overlap in your workflow early avoids a last-minute scramble.
Are there special rules for farmers, fishers, and fiscal-year taxpayers?
Yes, and these exceptions matter for a subset of clients. If at least two-thirds of a taxpayer's gross income for 2025 or 2026 comes from farming or fishing, the standard three-installment schedule does not apply. They may instead make a single estimated payment by January 15, 2027, or skip estimated payments entirely by filing their 2026 Form 1040 and paying in full by March 1, 2027.
Fiscal-year taxpayers use a different calculation entirely. Their four installment due dates fall on the 15th day of the 4th, 6th, 9th, and 12th months of their fiscal year. The rules are covered in detail in IRS Publication 505, Chapter 2. If you have a client whose tax year does not start January 1, confirm their specific due dates directly from Publication 505 rather than applying the calendar above.
What happens if a client misses a 2026 estimated tax deadline?
Missing a deadline does not create a separate failure-to-file penalty the way a missed annual return does. Instead, the IRS computes an underpayment penalty based on the federal short-term interest rate plus 3 percentage points, applied to the underpaid amount for each day it was short. The penalty accrues quarter by quarter, so a missed Q1 payment carries a larger penalty than a missed Q4 payment by the time the annual return is filed.
The practical advice for clients: pay as much as possible as soon as they realize they are behind. A partial payment made late reduces the base on which interest accrues. When the annual return is filed, Form 2210 is used to calculate the exact penalty; if income was front-loaded in a particular quarter, Schedule AI of Form 2210 may reduce or eliminate the penalty using the annualized method.
Disaster relief can also shift these deadlines. When the IRS grants relief for a federally declared disaster area, it typically postpones both filing and payment deadlines, including estimated payments. Check the IRS disaster relief announcements at IRS.gov whenever a natural disaster affects your client base.
How can your firm stay ahead of these deadlines without manual reminders?
Four estimated payment dates, four corresponding sets of client reminders, income projections to recalculate before each one — that cycle repeats every year and generates the same busywork each quarter. It's exactly the kind of recurring, rules-based task where an AI assistant removes the manual coordination overhead, freeing the same 30-45 minutes per client per quarter for actual advisory work. If you want to know which specific tools and automations make sense for your firm's size and software stack, a free CloseRadar operations audit maps that out in one short questionnaire — no sales call required.
On the practice management side, tools like TaxDome, Karbon, and Canopy all support recurring deadline tasks and client-facing reminders. You can also read about broader workflow automation options in the top accounting tasks to automate first and the roundup of the best AI tools for accountants. If your clients are also asking compliance questions about other 2026 filing requirements, the BOI report requirements for 2026 is worth bookmarking as well.
The most reliable system most small firms use is a combination of: a master deadline calendar visible to everyone on the team, a task in their practice management platform assigned 3-4 weeks before each date, and a client-facing reminder sent via their client portal 2 weeks out. That three-layer approach means a deadline never depends on one person's memory.