If you made money on the side in 2025 and didn't send the government anything quarterly, the bill landing in your mailbox right now is bigger than you planned for.
That's because the U.S. tax system runs on pay-as-you-go rules.
Employees have withholding quietly pulled from every paycheck.
Freelancers, gig drivers, Etsy sellers, and consultants don't get that courtesy — they're expected to send estimated payments four times a year, and the IRS charges interest on anything paid late.
The next deadline is June 16, which catches plenty of people off guard.
Many assume they only settle up in April.
By then, three quarters of the year have passed with nothing sent in.
Even if you file your return on time and get a refund, skipping quarterly payments can trigger an underpayment penalty.
The IRS treats it like a loan you took without asking.
The current rate on individual underpayments has hovered around 7% annually, and it compounds daily until you pay up.
Generally, if you expect to owe $1,000 or more for the year, the IRS wants money as you earn it.
That includes side hustles, rental income, investment gains, and freelance work — even if it's just a few thousand dollars a year.
Retirees drawing from 401(k)s without withholding can get hit too.
The good news is that catching up isn't complicated.
You can make a payment directly through IRS Direct Pay in a few minutes, no account required.
If you'd rather not guess, Form 1040-ES includes a worksheet, and most tax software will calculate the number for you.
A simple rule of thumb many accountants use: set aside 25% to 30% of every freelance check in a separate savings account.
When June 16 arrives, the money is already there instead of coming out of rent.
There's also a safe harbor worth knowing.
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 generally avoid the penalty, even if you end up owing more in April.
That's why some people just repeat last year's payment amount and adjust later.
Penalties are calculated on the unpaid amount and the clock, so every week you wait adds a little more.
The fee is usually modest for a one-time slip — the real damage comes from ignoring it for years.
One more trap: the IRS doesn't always send a friendly reminder.
If you owe and skip payments, you may not hear anything until a notice shows up months later with interest attached. **Our take:** The quarterly system is annoying, but it's not a trap if you plan for it.
Treat every payment you receive like it's 70% yours and 30% the government's, and June stops being a scare.
Final Thoughts
The people who get burned are almost always the ones who never ran the math.