If you earn money that doesn't come with a W-2, you've probably already circled September 15 on the calendar.
That's when the third-quarter estimated tax payment is due, and it catches people off guard every single year.
Here's the part that stings: you're paying tax on money you may have earned back in June, July, or August.
Waiting until April to settle up means you're paying late, and the IRS charges interest and penalties on the shortfall, not just the tax itself.
The rule of thumb is that you need to pay at least 90% of what you'll owe this year, or 100% of what you owed last year, whichever is smaller.
Miss both marks and you can get hit with an underpayment penalty even if you file on time and get a refund.
Freelancers, gig drivers, rideshare workers, small business owners, and anyone pulling in rental income or big investment gains.
Retirees with sizable 401(k) withdrawals land here too, because those accounts often don't withhold enough.
The simplest fix is the safe harbor trick.
If your income jumped this year, base your payments on last year's tax bill instead of guessing at this year's.
It's not always the cheapest option, but it protects you from penalties while you sort out the real numbers.
You can pay through IRS Direct Pay, your IRS online account, or the Electronic Federal Tax Payment System.
Direct Pay pulls straight from a checking account and costs nothing.
Third-party apps that charge a fee for the same service are not doing you a favor.
If you're behind, don't panic and don't ignore it.
You can adjust your remaining payments to catch up, and the penalty is calculated on how long you're short, so fixing it sooner costs less than fixing it in April.
A tax pro or free IRS Free File option can help you run the math.
One more thing people miss: if you have a regular job and a side hustle, you can raise your withholding at work instead of mailing quarterly checks.
It's the same money, but it comes out automatically and you're far less likely to forget.
Set a calendar reminder for January 15 too.
That's the last estimated payment for the 2025 tax year, and it arrives right after the holidays when nobody's thinking about the IRS.
Estimated taxes are not a punishment aimed at freelancers; they're just the pay-as-you-go version of withholding that regular employees never see.
Bite the bullet, pay what you can, and treat the quarterly deadline like any other bill.
Final Thoughts
Your future self in April will thank you.