If you're self-employed, a gig worker, or retired on investment income, the IRS isn't waiting until April.
Your next estimated tax payment is likely due September 15, and if you've been treating this like an optional chore, the penalty math gets ugly fast.
When you have a regular job, your employer quietly withholds taxes from every paycheck.
Nobody hands you a W-2 when you drive for a rideshare app or sell candles on Etsy.
The government still expects its cut, just in four installments instead of tiny automatic bites.
The rule of thumb is that you owe tax once you expect to owe at least $1,000 for the year.
Hit that threshold and the IRS wants quarterly payments covering your income and self-employment taxes—the latter running about 15.3% on top of your regular income rate.
Miss the deadlines and you're looking at underpayment penalties plus interest, even if you pay everything you owe in April.
The deadlines follow a calendar that trips people up: April 15, June 15, September 15, and January 15 of the following year.
Notice that gap between January and April.
That's not a break—it's the IRS collecting early so it isn't chasing you at filing time.
So how do you figure out the number without hiring an accountant?
The IRS offers a free worksheet in Form 1040-ES, and the safe harbor rules give you an out.
If you pay at least 90% of this year's tax or 100% of last year's (110% if your income topped $150,000), you dodge the penalty even if you guess low.
For many people, just repeating last year's total in four equal chunks is the simplest path.
If your income swings wildly—big months, dead months—the annualized income installment method lets you pay more in the quarters you actually earned more.
It's more paperwork, but it can shrink what you owe in a slow stretch.
Set aside a percentage of every payment you receive into a separate savings account so the money exists when the deadline hits.
If you also work a W-2 job, you can bump up your withholding there instead and skip the quarterly dance entirely.
And if you're short this quarter, paying something beats paying nothing—the penalty scales with how much you underpaid and for how long.
Most states with income tax run their own estimated payment schedules, and a federal payment doesn't cover you.
Check your state's revenue department site, because some deadlines differ by a few days or weeks.
The whole system rewards people who plan and punishes people who don't.
That's not a moral judgment—it's just how the code is written.
Set a calendar reminder for September 15, run your numbers, and send what you can.
If you're consistently getting hit with penalties, that's a signal your withholding or estimates are set too low all year, not that the IRS is out to get you.
Final Thoughts
Fix the setting once and the surprise disappears.