Estimated Taxes Due September 15: What Freelancers and the Self-Employed Need to Know

If you're self-employed, freelance, or drive for a gig app, September 15 is the deadline for your third-quarter estimated tax payment, covering income you earned between June 1 and August 31. Miss it, and the IRS can charge you a penalty even if you pay everything in full come April.

That catches a lot of people off guard. Nobody's taking taxes out of your pay when you're 1099, so it's easy to treat the number in your bank account as yours to spend. Then September rolls around and there's a deadline nobody told you about.

Here's what you actually need to know.

Do I Even Need to Pay Estimated Taxes?

Probably, if you expect to owe at least $1,000 in federal tax for the year after subtracting whatever's already been withheld. That's the IRS's own threshold, and it covers most freelancers, gig workers, and small business owners who don't have an employer taking taxes out for them.

W-2 employees usually don't need to worry about this. Their employer withholds throughout the year. But the moment you add freelance income, a side business, or gig work on top of a regular job, you might owe more than what's being withheld from your paycheck alone.

What Exactly Is Due on September 15?

Estimated taxes get paid in four chunks across the year, not one lump sum. For 2026, the schedule looks like this: April 15 for Q1, June 15 for Q2, September 15 for Q3, and January 15, 2027 for Q4.

September 15 covers income earned from June through August. It's not a deadline for the whole year, just that one stretch.

How Much Should I Actually Send?

This is where people get stuck, so here's the simple version: figure out your safe harbor number, then send a quarter of it, minus whatever you've already paid this year.

You're in the clear on penalties if you pay one of these two amounts across the year:

• 100% of what you owed last year (110% if your 2025 adjusted gross income was over $150,000), or

• 90% of what you'll actually owe this year

Most freelancers use the prior-year number because it's the one you can actually calculate today. Take last year's total tax bill, apply the 100% or 110% rule, divide by four, and that's roughly your quarterly target.

What If I Already Missed a Payment This Year?

Catching up now still helps. The IRS calculates the underpayment penalty quarter by quarter, so a payment made today doesn't erase a gap from April or June, but it stops the bleeding for this quarter and the ones ahead. Waiting until next April to "true up" everything at once is the version that costs the most.

What Happens If I Miss September 15 Entirely?

You'll owe an underpayment penalty, calculated using the IRS's quarterly interest rate on whatever you were short. It's not a flat fine. It compounds the longer the shortfall sits unpaid, which is exactly why catching it in September is cheaper than catching it in April.

What If I Have No Idea What I'll Owe?

That's normal, especially in your first year of self-employment. A rough estimate paid on time beats a perfect number paid late. If your income has been irregular this year, this is worth a quick call rather than a guess. We can run your numbers against both the prior-year and current-year safe harbor methods and tell you which one actually saves you money.

The One-Sentence Version

If you're self-employed and expect to owe $1,000 or more this year, get a payment in by September 15. Base it on last year's tax bill if you're not sure what else to use, and don't wait until April to find out you guessed wrong three times in a row.