Roughly 23 million self-employed Americans owe the IRS money four times a year, and a surprising number of them are quietly paying the wrong amount.
The next estimated tax deadline lands on September 15, covering income earned from June through August.
Miss it, and the IRS can tack on a penalty that accrues daily — even if you plan to pay everything in full next April.
The confusion starts with a system built for paychecks, not gig work.
Nobody withholds anything for a rideshare driver, a freelance designer, or a consultant billing by the hour.
The rule of thumb: if you expect to owe $1,000 or more for the year, the IRS wants quarterly payments.
That threshold catches far more people than most realize — a single decent side hustle can push you over it.
There are two safe ways to calculate what you owe.
The first is the prior-year method: pay 100% of last year's tax bill in four equal chunks, or 110% if your adjusted gross income topped $150,000.
The second is the annualized method, which tracks income quarter by quarter and works better if your earnings swing wildly.
Picking the wrong method is where penalties creep in.
The prior-year approach is simpler but can leave you short if business picked up.
The annualized route takes more paperwork but often lowers the bill for people with lumpy income.
One detail that trips up almost everyone: the IRS operates on a pay-as-you-go system.
If you land a big client project in July and pay nothing until April, you owe interest on the delay — regardless of whether your total tax bill is correct.
The fastest fix is to log into IRS Direct Pay or your IRS online account.
Both let you schedule a payment, see your history, and avoid the third-party fees that payment apps quietly charge.
If you're short on cash, the agency offers installment plans, and the penalty for underpayment is currently running around 7% annually — painful but not catastrophic.
Ignoring the notice is what turns a small balance into a lien.
A quick gut check: look at last year's return, find your total tax line, and divide by four.
If you've already paid more than that, you're likely fine.
If not, September is your chance to catch up before the January deadline stacks on top.
It's the assumption that taxes are an April problem.
For anyone earning without a W-2, they're a September problem, a January problem, and a June problem too.
Our take: the quarterly system punishes people for having irregular income, which is exactly the kind of income a growing share of Americans now earn.
Automating a payment every quarter — even a rough estimate — beats scrambling later.
Final Thoughts
Set a calendar reminder for September 15 and treat it like any other bill.