If you're self-employed, an investor, or a landlord, the IRS expects you to pay tax four times a year — not just at filing time. Hit any one of the safe-harbor rules (pay 90% of this year's tax, or 100% of last year's — 110% if your AGI is over $150K) and the underpayment penalty disappears.
"Quarterly estimated taxes" sounds like one of those terms designed to make people feel bad about themselves. But once you understand the safe-harbor rule, the whole thing takes about 20 minutes per quarter — and you'll never have to scramble for a five-figure check on April 15 again.
Why these exist in the first place
The U.S. has a "pay-as-you-go" tax system. If you're a W-2 employee, your employer withholds tax from each paycheck so by year-end you're roughly caught up. If you earn money without withholding — freelancing, rental income, capital gains, S-Corp distributions — the IRS still wants its share during the year, not after. So they ask you to estimate and prepay, four times a year.
Skip the prepayments and you'll owe an underpayment penalty. As of 2026 the rate is roughly 8% annualized — effectively interest charged from the date each quarterly payment was due.
Who actually has to pay them
The general rule: you owe estimates if you expect to owe $1,000 or more at filing time after subtracting withholding and credits. In practice, this catches:
- Self-employed people filing Schedule C
- S-Corp shareholders whose payroll withholding doesn't cover the K-1 income
- Partners receiving K-1s from a 1065
- Landlords with profitable rentals (Schedule E)
- Anyone with significant interest, dividend, or capital gains income
- Retirees who turned off withholding on Social Security or IRA distributions
The safe harbor — the only math you need
You don't actually have to predict this year's tax perfectly. You just have to hit one of three targets, called safe harbors:
- Pay at least 90% of this year's total tax, OR
- Pay at least 100% of last year's total tax, OR
- If your prior-year AGI was over $150,000, pay 110% of last year's total tax
For most clients, target #2 (or #3) is the simplest. You already know last year's number — it's on line 24 of your 1040. Divide by four, and pay that each quarter.
Example: Last year you owed $30,000 in total federal tax and your AGI was under $150K. Pay $7,500 per quarter in 2026 and you're safe-harbored, no matter how much you actually end up making this year. Owe $80K at filing time? No penalty.
The 2026 due dates
Quarterly is a misnomer — the periods aren't equal. Mark these:
- Q1 (Jan–Mar income): April 15, 2026
- Q2 (Apr–May income): June 15, 2026
- Q3 (Jun–Aug income): September 15, 2026
- Q4 (Sep–Dec income): January 15, 2027
Missouri (and most states) follow the same schedule with their own voucher (Form MO-1040ES). State estimates are paid separately.
How to actually pay
Don't mail a check. Pick one of these:
- IRS Direct Pay (irs.gov/directpay) — free, instant, no account needed. Pulls from your bank account. Our default recommendation for individuals.
- EFTPS (eftps.gov) — free, but enrollment takes 5–7 business days for a mailed PIN. Worth it if you're paying estimates and payroll taxes for a business.
- IRS2Go app — same as Direct Pay, on your phone
- Card — works, but you'll pay a 1.8–2.0% processing fee. Usually not worth it unless you're chasing card rewards.
Whichever you use, pick the right tax year and "estimated tax (Form 1040-ES)" as the reason. Save the confirmation number with your records.
What happens if you miss one
Don't panic. The penalty is calculated quarter-by-quarter, so a missed Q1 doesn't blow up your whole year — interest just runs from April 15 until you make up the shortfall. Pay as soon as you remember and the bleeding stops.
A single skipped quarter on a $7,500 payment, caught about two months late, usually runs $80–120 in penalty. Annoying, not disastrous. The real problem is skipping all four and then owing $30K in April with no cash on hand — that's the situation we help clients avoid.
An $80 underpayment penalty stings far less than scrambling for a $30,000 surprise in April. Steady wins.
Smarter habits we recommend
- If you're an S-Corp owner, raise your payroll withholding instead. Withholding is treated as paid evenly across the year — much more forgiving than estimated payments.
- Set up an auto-transfer to a separate "tax savings" account each time you get paid. Roughly 25–30% of net profit for most self-employed clients. The money is there when the voucher is due.
- Recheck mid-year if income spikes. Big consulting contract or unexpected capital gain? We re-project so you're not safe-harbored to an artificially low prior-year number while owing way more in reality.
- Working with a CPA? We send you a payment voucher with the exact amount and a one-click link each quarter — about as headache-free as it gets.
If you've never paid quarterly estimates and suspect you should be, the next deadline is the right place to start. Reach out for a free 20-minute consultation and we'll calibrate from there.