If you own a business, freelance, or earn income that is not covered by paycheck withholding, your Q3 estimated taxes are due Monday, September 15, 2026. This is the third of four quarterly estimated tax payments the IRS expects during the year, and missing it can trigger penalties even if you eventually pay in full. Here is a plain-English guide to who owes, how much to pay, and how to send it in before the deadline.
When are Q3 estimated taxes due in 2026?
Third-quarter (Q3) estimated taxes for 2026 are due September 15, 2026. The IRS splits the year into four uneven payment periods, and the September payment covers income you earned from June 1 through August 31. For reference, the full 2026 schedule is:
- Q1: April 15, 2026 (income from January 1 to March 31)
- Q2: June 15, 2026 (income from April 1 to May 31)
- Q3: September 15, 2026 (income from June 1 to August 31)
- Q4: January 15, 2027 (income from September 1 to December 31)
Because September 15 falls on a business day this year, there is no extension of the deadline. Payments are considered on time if they are postmarked or submitted electronically by that date.
Who has to pay quarterly estimated taxes?
You generally need to pay quarterly estimated taxes if you expect to owe at least $1,000 in tax for the year after subtracting withholding and credits. Because the U.S. tax system is pay-as-you-go, the IRS wants tax collected as you earn, not just at filing time. That most often includes:
- Sole proprietors, freelancers, and independent contractors
- Owners of S corporations and partnerships whose profits pass through to their personal return
- Single-member LLC owners reporting business income on Schedule C
- Anyone with significant income from investments, rentals, or side work with no withholding
If you are a W-2 employee with a side business, you can sometimes cover the extra tax by increasing withholding at your job instead of making separate quarterly payments.
How do I calculate my Q3 estimated tax payment?
Estimate your total expected tax for the year, then pay roughly one quarter of it each period, adjusting for what you have already paid. Self-employed owners should remember the payment covers two things: federal income tax at your bracket and the 15.3% self-employment tax (Social Security and Medicare). A practical approach:
- Project your net business profit for the full year
- Apply your expected income tax rate plus the 15.3% self-employment tax
- Subtract any withholding and payments already made for Q1 and Q2
- Divide the remaining amount across the periods still due
Many owners simply set aside 25% to 30% of net profit as they go so the cash is ready each quarter. Getting the number right depends on clean, current books, which is exactly the kind of ongoing support our Tax & Compliance services provide so you are never guessing at a deadline.
How do I pay estimated taxes to the IRS?
The fastest way to pay is online through IRS Direct Pay or the Electronic Federal Tax Payment System (EFTPS), both free and available on IRS.gov. Your options include:
- IRS Direct Pay — pay directly from a checking or savings account with no account setup
- EFTPS — a free enrolled system that works well for businesses making regular payments
- Debit or credit card — allowed through approved processors, though card fees apply
- Mail — a paper check with a Form 1040-ES voucher
Don't forget your state. Minnesota and most other states have their own quarterly estimated payments, often due on the same September 15 date, and they are paid separately from your federal payment.
What happens if I miss the September 15 deadline?
If you miss the deadline or pay too little, the IRS charges an underpayment penalty that works like interest on the shortfall for each period you were behind. It is not a flat fine, so the sooner you pay after a missed deadline, the smaller the penalty. Two things worth knowing:
- Paying a lump sum next April does not erase penalties already building for earlier quarters, so it is better to pay late than not at all.
- You can avoid the penalty entirely by meeting a safe harbor: paying at least 90% of this year's tax or 100% of last year's tax (110% if your prior-year income was over $150,000).
If cash flow is tight, make the largest payment you reasonably can by September 15 to limit the penalty, then plan ahead so Q4 in January is not another scramble.
Quarterly taxes are one of the most common places small business owners get tripped up, and a missed or miscalculated payment quietly costs money all year. If you would rather stop guessing, we can build a simple system that tells you exactly what to set aside and when to pay it.