Q3 Estimated Tax Payment: A Quick Guide
September brings back-to-school lists, cooler mornings and, for many self-employed people in the US, the third estimated tax payment of the year. If you earn income that has no tax withheld, this guide walks you through what the Q3 payment covers, how to size it without panic and how to get it paid on time with a few calm hours of prep in late August.
Key takeaways
- The US Q3 estimated tax payment for 2027 is due on 15 September 2027 and generally covers income earned in the summer months.
- You can size the payment from your year-to-date profit, from last year's tax, or both. Pick one method and write down how you used it.
- Paying online through the IRS is usually the fastest route, and it gives you a confirmation you can save.
- Setting aside a fixed share of every payment you receive makes each quarter far less stressful.
Estimated taxes feel intimidating mainly because nobody sends you a bill. An employer withholds tax from a paycheck automatically, but when you run a sole proprietorship, a single-member LLC, a side hustle or a partnership, that job falls to you. The IRS expects tax to be paid as income is earned during the year, not all at once in April, and the quarterly estimated payment system is how that happens.
The good news is that the Q3 payment is the easiest one to get right. You already have more than half a year of real numbers, the summer is mostly behind you and you still have time to adjust before the year closes. Let's make it simple.
A quick note before we start: this article is general information, not tax advice. Rules, forms and due dates can change, so check IRS.gov for the current year and speak with a tax professional about your own situation.
What the Q3 estimated tax payment is
US estimated tax is paid in four installments across the year. Each installment covers a slice of the year's income, though the slices are not equal quarters. The third payment, due in mid-September, generally covers income earned over the summer months. It typically includes both federal income tax and, if you are self-employed, self-employment tax for Social Security and Medicare.
Who usually needs to pay
You may need to make estimated payments if you expect to owe tax that is not covered by withholding. Common examples include:
- Freelancers and independent contractors paid without withholding.
- Sole proprietors and single-member LLC owners whose profit flows through to their personal return.
- Partners and S-Corp shareholders with income passing through from the business.
- Side hustlers earning from marketplace sales, rentals or consulting on top of a salaried job.
- Investors with significant interest, dividends or capital gains.
The IRS has a threshold for when estimated payments are required, and it can change. Rather than guessing, check the current Form 1040-ES instructions or ask your accountant whether it applies to you.
Why it matters if you skip it
If you underpay during the year, the IRS may charge an underpayment penalty, calculated much like interest for the time the money was late. You will still owe the tax itself in April. Paying each quarter keeps penalties away and, just as usefully, stops one enormous bill from landing all at once.
Key dates to put on your calendar
The Q3 date sits in a busy stretch of the year, which is exactly why it gets missed. Here is how the late summer lines up in 2027:
- Late August: close your books through the end of August so your numbers are fresh.
- Monday 6 September 2027: US Labor Day. Banks and many offices close, so do not plan to pay that day by mail.
- Wednesday 15 September 2027: the Q3 estimated tax payment is due.
Your state may also require estimated payments on its own schedule. Many states follow similar dates, but not all of them do, so check your state tax agency's site as well.
Pro tip
Set two reminders, not one. The first, around 1 September, tells you to run the numbers. The second, a few days before the due date, tells you to press pay. Having that buffer leaves room for a bank login that misbehaves or a missing statement.
How to work out your Q3 amount
There are two common ways to size an estimated payment. Many people use a mix: a quick check based on last year, then a more careful look at this year's actual profit.
Method 1: base it on last year's tax
The IRS offers "safe harbor" rules that can protect you from underpayment penalties if your total estimated payments and withholding reach a certain share of last year's tax. The exact percentage depends on your income, so check the current Form 1040-ES instructions. This method is predictable and simple: you divide the target into four installments and pay the same amount each time.
The catch is that it protects you from penalties, not from a large balance due. If your business has grown a lot this year, you may still owe a big amount in April.
Method 2: base it on this year's actual profit
This method uses your real year-to-date numbers. It takes a little more work but matches your tax more closely, which is useful if your income jumps around.
- Close your books through August. Record every sale and expense, and reconcile your bank and card accounts.
- Find your year-to-date profit. Revenue minus deductible business expenses for January to August.
- Project the full year. Add a realistic estimate for September to December. Use last year's pattern or your current pipeline, not your hopes.
- Estimate the full-year tax. Apply your expected income tax and self-employment tax. Tax software or your accountant can do this part quickly.
- Subtract what you have paid. Take away Q1 and Q2 payments and any withholding from a salaried job.
- Split the remainder. Divide what is left between the Q3 and Q4 payments, or pay more now if cash allows.
Example
Imagine Marco, a freelance web developer. By the end of August his year-to-date profit is $54,000 and he expects about $24,000 more by December. His accountant estimates his full-year federal tax at $19,500. He has already paid $4,500 in Q1 and $4,500 in Q2, so $10,500 remains. He splits it into $5,250 for Q3 and $5,250 for Q4 in January. (All numbers are made up for illustration.)
Common mistake
Copying the Q1 amount into Q3 without looking at the numbers. If your summer was much stronger or weaker than spring, the old figure can be badly off. Ten minutes with your year-to-date profit is worth it.
A simple Q3 estimate worksheet
Copy this table into a spreadsheet. Fill in one row per line item and keep the sheet with your tax records so you can explain how you reached the figure.
| Line item | Example amount (made up) | Where it comes from | Notes |
|---|---|---|---|
| Year-to-date profit (Jan to Aug) | $54,000 | Profit and loss report | After reconciling all accounts |
| Projected profit (Sep to Dec) | $24,000 | Pipeline and last year's pattern | Use a cautious figure |
| Estimated full-year tax | $19,500 | Tax software or accountant | Income tax plus self-employment tax |
| Paid so far (Q1 + Q2) | $9,000 | Payment confirmations | Include any withholding |
| Q3 payment | $5,250 | Half of the remaining balance | Due 15 September 2027 |
If you also pay state estimated tax, add a second block underneath with the same columns. Keeping federal and state side by side stops one from being forgotten.
How to pay the IRS
Once you have your figure, paying is the easy part. The IRS offers several ways to pay estimated tax, and the online options are usually the fastest and leave a clear record:
- IRS online payment options: you can pay directly from a bank account through the IRS website, or through your IRS online account, and get a confirmation number.
- The federal electronic tax payment system: useful if you like scheduling payments ahead of time. It requires enrollment, so set it up well before the deadline.
- Debit or credit card: available through approved processors, which charge their own fees. Check the cost before you choose this route.
- Check by mail: sent with the payment voucher from Form 1040-ES. Allow plenty of time and keep proof of mailing.
Whichever you choose, make sure the payment is marked as an estimated tax payment for the right tax year. Save the confirmation as a PDF in your tax folder with a clear name such as "2027 Q3 federal estimate".
Pro tip
Pay from the account where you hold your tax savings. That keeps your operating account untouched and makes reconciliation simple: the money left the tax pot, went to the IRS and the books match.
Making next quarter easier
The Q3 payment is a good moment to fix your system for the rest of the year. A few habits make estimated tax almost boring.
Set aside tax as you earn
Many freelancers move a fixed percentage of every client payment into a separate tax savings account the day it arrives. The right percentage depends on your income, deductions and state, so ask your accountant for a sensible figure. Once the habit is in place, each quarterly payment is simply a transfer from money that was already put aside.
Close your books monthly
If you reconcile your accounts once a month, running a quarterly estimate takes minutes rather than a weekend. Monthly closes also catch missing invoices and duplicate charges while they are still easy to fix.
Watch for big swings
A large one-off contract, the sale of equipment or a sudden slow month can change your tax picture. When something big happens, rerun the worksheet instead of waiting for the next deadline.
A note for readers outside the US
The UK and many European countries handle tax on self-employment differently. In the UK, self-employed people under Self Assessment may make payments on account rather than quarterly estimates, on dates set by HMRC. If you live outside the US, check your own tax authority's guidance, and if you have income in more than one country, a cross-border tax adviser is worth the fee.
Common mistake
Spending the tax money in a slow month and hoping to catch up later. It rarely works. If cash is tight, pay what you can on time and talk to your accountant about the rest, rather than paying nothing at all.
Your Q3 estimated tax checklist
- Add 15 September 2027 and a reminder on 1 September to your calendar
- Close and reconcile your books through the end of August
- Pull your year-to-date profit and project September to December
- Estimate full-year tax with your software or accountant
- Subtract Q1, Q2 and any withholding, then set the Q3 amount
- Check whether your state needs its own estimated payment
- Pay online and save the confirmation in your tax folder
- Review your tax savings percentage for the rest of the year
Frequently asked questions
What if I miss the Q3 deadline?
Pay as soon as you can. Underpayment penalties are generally based on how long the money was late, so a few days late costs less than a few months late. Then set stronger reminders for the January payment.
Can I pay more than one quarter at once?
Yes. You can make extra or larger payments at any time. Some people pay ahead after a strong month so the cash is not tempting. Just make sure each payment is applied to the right tax year.
My income dropped this summer. Can I pay less?
Often, yes. If your projected tax is lower, your remaining payments can be lower too. Run the worksheet with your real numbers and keep a note of how you worked it out. Your accountant can confirm whether a lower payment still keeps you clear of penalties.
Do I need an accountant for estimated taxes?
Not always. Many freelancers handle it with tax software and good bookkeeping. An accountant is worth it if your income is complex, you have several income sources, or you want help choosing the right safe harbor approach.
Related reading
The bottom line
The Q3 estimated tax payment is due on 15 September 2027, and a little preparation in late August makes it painless. Close your books, choose a method, fill in the worksheet, pay online and save the proof.
Do it once with care and you will have a repeatable routine for January and every quarter after. That steady rhythm is what turns tax season from a shock into just another task on your list.
