The next estimated tax payment deadline is September 15, and if you're one of the millions of people who owe money this quarter, missing it can get expensive fast.
The IRS doesn't send a friendly reminder before charging a penalty.
Estimated taxes aren't just for the self-employed anymore.
If you picked up a side hustle, sold stocks, earned freelance income, or collected rental payments this year, you may owe quarterly payments even though you also have a regular job with taxes taken out.
You generally need to pay at least 90 percent of what you'll owe for the year, or 100 percent of what you owed last year, whichever is smaller.
If you fall short, the penalty is calculated as interest on the underpaid amount.
It's not a flat fine, but it adds up the longer you wait.
The penalty rate has been hovering around 7 to 8 percent annually in recent years, which is higher than it was for most of the past decade.
On a $3,000 shortfall, that's real money leaving your pocket for no good reason.
The tricky part is knowing whether you qualify.
A common rule of thumb: if you expect to owe less than $1,000 when you file your return, you're usually in the clear.
If you owe more than that, or if you didn't have enough tax withheld from your paycheck, the IRS wants quarterly payments.
One easy fix many people overlook is adjusting their W-4 at work.
You can ask your employer to withhold extra from each paycheck to cover side income, which means you never have to remember a quarterly deadline at all.
If you miss September 15, don't panic and don't skip it entirely.
The penalty grows by the day, so paying late is still better than not paying.
You can pay through IRS Direct Pay, your IRS online account, or by debit and credit card, though card payments come with processing fees.
Setting a calendar reminder for January 15, the next deadline after this one, takes about ten seconds and can save you hundreds.
The people who get hit hardest are usually first-timers: the newly self-employed, the side-gig worker, the person who cashed out an old 401(k).
Nobody warns them, and the penalty shows up quietly on next year's return.
Bottom line: if your income changed this year in any way, spend five minutes checking whether you owe a quarterly payment.
It's one of the cheapest financial chores you can do, and ignoring it is one of the most expensive.
Final Thoughts
Set the reminder, make the payment, and move on with your week.