If you earn money without an employer withholding taxes, the calendar has a way of sneaking up on you.
Four times a year, the IRS expects a payment on income that hasn't had a single dollar set aside.
Miss one, and the penalty shows up quietly on next year's return.
The next deadline is September 15 for anyone on the quarterly schedule.
That covers income earned from June 1 through August 31.
The other three dates to circle are April 15, June 15, and January 15 of the following year.
Freelancers, gig drivers, consultants, landlords, small business owners, and anyone pulling in side income that isn't taxed at the source.
If you expect to owe at least $1,000 for the year, the IRS generally wants you paying as you go rather than in one lump sum come April.
The penalty is not dramatic, but it is real.
The IRS charges interest on underpayments, and the rate has been running around 7% to 8% in recent quarters.
On a $5,000 shortfall, that's real money that buys nothing.
Many assume they can just pay whatever they can afford each quarter and square up later.
That works only if you hit one of the safe harbors.
You're generally protected if you pay at least 90% of this year's tax bill or 100% of last year's, whichever is smaller.
High earners above $150,000 need to cover 110% of last year's number.
The simplest fix is the annualized income method for people with uneven earnings.
If you made almost nothing in January but had a monster July, the standard four-equal-payments approach can overstate what you owed early in the year.
Form 2210 lets you match payments to when the money actually came in.
A second trap: forgetting self-employment tax.
That's 15.3% on top of regular income tax, covering Social Security and Medicare.
New freelancers often budget for income tax only, then get blindsided.
If you have a W-2 job on the side, you can dodge the whole quarterly routine.
Ask your employer to withhold extra from each paycheck using a revised W-4.
The IRS treats withholding as paid evenly through the year, which can erase a penalty even if you catch up in December.
Setting the money aside is the unglamorous part.
A common approach is moving 25% to 30% of every payment into a separate savings account the day it lands.
That way the quarterly bill never touches your rent money.
You can pay online through IRS Direct Pay, by debit or credit card, or through your IRS online account.
Credit card payments carry a processing fee, usually around 2%.
Mailing a check still works, but the postmark rules matter and the IRS has been slow on paper processing.
Online is faster and gives you a receipt the same day.
If you've fallen behind, you don't have to fix it all at once.
The IRS offers installment plans, and in many cases the setup fee is waived for lower-income filers.
Ignoring the notices is what turns a manageable bill into a bigger one. **Our take:** The quarterly system punishes people for a cash-flow problem, not a tax-dodging one.
If you're self-employed, treat those four dates like rent — automatic, non-negotiable, and funded before the money ever feels spendable.
Final Thoughts
Ten minutes of setup now beats an ugly surprise in April.