If you started freelancing, driving for a rideshare, or selling online this year, the IRS expects a check four times a year—not once in April.
Miss those dates and the penalty compounds quietly, no matter how honest your mistake was.
The next estimated tax deadline is September 15.
It covers income you earned from June through August.
If you got a 1099 instead of a W-2, nobody withheld taxes from that money.
Here's the part that trips people up: the IRS doesn't care that you'll "settle up later." Underpayment penalties accrue daily at roughly 7% to 8% annually right now, and they're calculated from the moment each installment was due.
Wait until filing season and you've handed over months of interest for free.
The rule of thumb is to pay either 90% of what you owe this year or 100% of last year's total tax—110% if your adjusted gross income topped $150,000.
Hitting that safe harbor protects you from penalties even if you guess low.
Common mistakes: assuming a side hustle under a few thousand dollars doesn't count, forgetting that DoorDash and Etsy income is fully taxable, and skipping the state payment.
Most states with income tax run their own quarterly system on similar dates.
If you had a W-2 job too, you can often dodge quarterly payments entirely by bumping up withholding on your paycheck.
Adjust your W-4 and let the extra come out automatically—it counts as paid evenly across the year, which quarterly payments don't.
Freelancers with uneven income can use the annualized income installment method to pay less in quarters when they earned less.
It takes more paperwork but can cut a penalty that would otherwise be based on a flat four-way split.
Set aside 25% to 30% of every payment you receive into a separate savings account the day it lands.
When the deadline hits, the money is already there.
That single habit separates people who dread tax season from people who barely notice it.
You can pay through IRS Direct Pay, your IRS online account, or EFTPS.
Same-day options exist if you're late and scrambling.
The IRS also offers a free tax withholding estimator that takes about ten minutes and tells you exactly what to send.
One more thing: if you're behind on earlier quarters, pay the oldest first.
Penalties stack per period, and clearing the oldest installment stops the meter on that one. **Our take:** The tax code rewards people who pay attention quarterly and quietly punishes everyone else.
Final Thoughts
If you earn 1099 income, treat September 15 like a real deadline—because the IRS absolutely will.