If you're self-employed, a freelancer, a landlord, or anyone earning meaningful income without tax withholding, the IRS expects you to pay tax as you earn it — not in one big check on April 15. That's what estimated quarterly taxes are for.
Get the rhythm right and they're a non-event. Get it wrong and you owe penalties plus interest on top of the tax. Here's how to handle them without the dread.
Who Actually Has to Pay
The IRS rule: you owe estimated taxes if you expect to owe at least $1,000 in tax for the year after subtracting withholding and refundable credits.
If you're a W-2 employee with a side hustle, you have two options:
- Pay quarterly estimated taxes on the side income, OR
- Increase withholding on your W-2 (file a new W-4 with extra withholding) to cover the side-income tax. This is simpler and avoids any quarterly paperwork.
The Four Due Dates
Estimated taxes are due four times a year, on uneven quarters:
- Q1 (Jan 1 – Mar 31): due April 15
- Q2 (Apr 1 – May 31): due June 15
- Q3 (Jun 1 – Aug 31): due September 15
- Q4 (Sep 1 – Dec 31): due January 15 of the next year
Note that 'Q2' is only two months long. The IRS calendar is not your calendar.
Two Ways to Calculate
Method 1: Safe Harbor (the easy way)
Pay 100% of last year's total tax (110% if your AGI was over $150,000), divided into four equal payments. As long as you hit that number, the IRS won't charge underpayment penalties — no matter how much you actually owe at the end of the year.
This is the move for anyone whose income is unpredictable. You're protected from penalties even if you have a huge year.
Method 2: Pay as you go
Each quarter, project year-to-date income, calculate the tax on it, and pay the difference between what you've paid so far and what you should have paid by now. More accurate, but more work, and you have to redo the math every quarter.
How to Actually Pay
Three options, all easy:
- IRS Direct Pay (irs.gov/payments) — free, takes 5 minutes, pulls from your bank account.
- EFTPS (eftps.gov) — slightly more setup but lets you schedule future payments.
- Mail Form 1040-ES with a check. Slow, but it works.
Don't forget state estimated taxes — Mississippi has its own quarterly schedule. Most states match the federal dates.
A Simple System That Works
Open a separate savings account labeled 'Taxes.' Every time money hits your business account, transfer 25–30% to the tax account. When quarterly due dates arrive, pay from the tax account. You'll always have the money, and you'll stop thinking of tax as something that comes out of 'your' money — because it never was.
What Happens If You Underpay
The IRS charges an underpayment penalty (effectively interest at the federal short-term rate plus 3%). For 2025, that's roughly 8% annualized on the underpaid amount, charged per quarter. Not catastrophic, but not free either.
If you miss a quarter, just pay as soon as you can — the penalty stops accruing once the payment lands.
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