If you made money this year without an employer withholding it, the IRS is expecting a check.
The next estimated tax deadline is September 15, and it covers income you earned from June through August.
Miss it, and the penalty math starts working against you fast.
Here's the part that trips people up: the US tax system runs on pay-as-you-go rules.
Employees have taxes pulled from every paycheck.
Freelancers, gig workers, rideshare drivers, and anyone earning from side hustles have to send that money in themselves, four times a year.
The remaining 2025 deadlines are September 15 and January 15, 2026.
If you skip a payment or send too little, the IRS tacks on an underpayment penalty.
As of late 2025, that rate is running around 7% annually, compounded daily.
On a $5,000 shortfall, that's real money leaking out for no good reason.
If you expect to owe at least $1,000 for the year and your withholding covers less than 90% of this year's tax bill (or 100% of last year's, whichever is smaller), you're in the club.
That catches a lot of people who picked up a side gig, sold stock, or started collecting freelance checks on top of a regular job.
The good news is you don't need a CPA to stay out of trouble.
You can pay directly at IRS Direct Pay from a bank account, or set up an IRS Online Account to schedule payments ahead of time.
Credit card payments are also accepted through third-party processors, but they tack on a convenience fee of roughly 1.85% to 2%, which can wipe out your credit card rewards.
If you're not sure what you owe, IRS Form 1040-ES includes a worksheet that walks you through the estimate.
A simpler shortcut: if your income is steady, take your total expected tax liability and divide by four.
If your income swings wildly, the "annualized income installment method" lets you pay more in the quarters you actually earned more.
If you had a refund last year or you're juggling a W-2 job alongside freelance work, you can ask your employer to withhold extra from your regular paycheck.
Bumping your W-4 withholding is often the easiest fix, because it spreads the pain across every pay period instead of leaving you with a lump sum due.
It's the scramble in April when a freelancer realizes they owe thousands and has no cash set aside.
Setting aside 25% to 30% of every payment you receive is a boring habit that prevents an ugly surprise.
Our take: the quarterly system isn't designed to punish self-employed workers, but it absolutely will if you ignore it.
Fifteen minutes on the IRS website now beats a penalty notice and a panic attack later.
Final Thoughts
If you're unsure about your numbers, a one-time session with a tax pro usually costs less than the penalty you're trying to avoid.