If you earned money this year and nobody withheld taxes from it, the IRS is already expecting a cut.
Freelancers, gig drivers, rideshare workers, small business owners, and anyone pulling in side income usually have to pay estimated taxes four times a year — not once in April.
The next quarterly deadline lands on September 15.
Miss it and the IRS can tack on a penalty, even if you plan to square up when you file your return next spring.
The IRS doesn't care that you're busy or that your income is uneven.
It wants a slice of what you made during specific windows of the year.
Pay too little, too late, and the underpayment penalty stacks up quietly in the background.
The good news is the math is less scary than it sounds.
Most people owe either 90% of this year's tax bill or 100% of last year's — whichever is smaller.
That second option is a safety net if your income jumped and you can't predict where you'll land.
If your side hustle brought in a few hundred dollars, you may not owe anything.
The IRS generally wants estimated payments once you expect to owe $1,000 or more for the year.
Below that threshold, you can usually just settle up at filing time.
The IRS offers a free Direct Pay tool on its website that pulls straight from your bank account.
You can also schedule payments in advance, which is a lifesaver if you tend to forget deadlines.
Mail-in vouchers still exist, but they're slow and easy to lose.
If you have a regular job and a side gig, there's an easier fix.
Ask your employer to withhold extra from each paycheck by filing a new W-4.
That way the taxes come out automatically and you skip the quarterly guesswork entirely.
One more thing worth knowing: if you live in a federally declared disaster area, the IRS often pushes deadlines back automatically.
Check the agency's tax relief page before you send money — you might have extra time you didn't know about.
The penalty for underpaying isn't enormous, but it's avoidable.
It works out to roughly the federal short-term interest rate plus a few points, charged on the amount you should have paid.
On a few thousand dollars, that's real money that could've stayed in your pocket.
Even a partial payment before September 15 shrinks the penalty compared to paying nothing at all.
The tax system rewards people who plan ahead and punishes the ones who don't.
Final Thoughts
If you're earning extra income, spending fifteen minutes with the IRS Direct Pay tool this week beats a surprise bill in April.