Four dates. No April surprise.
The quick reference for the pay-as-you-go system: the four federal deadlines, the two safe-harbor methods that avoid the penalty, and the common questions, all on one page.
The 4 quarterly deadlines.
Two ways to avoid the penalty.
Method 1: 100% of last year
Pay 100% of last year's total tax bill (110% if AGI > $150K). Simplest if your income is similar year-over-year.
Method 2: 90% of current year
Pay 90% of what you'll actually owe this year. Better if your income is dropping.
Common questions.
Do I need to pay quarterly estimated tax?
Generally yes if you expect to owe $1,000+ in tax for the year (after withholding/credits). Common for self-employed, freelancers, LLC/S-Corp owners, investors with capital gains.
What is the underpayment penalty?
Calculated quarter-by-quarter at the federal short-term rate + 3%. Recent rate around 8% annualized.
What about state quarterly taxes?
Most states with income tax require their own quarterly payments. Some align with federal dates; some have different schedules.
How do I pay?
Federal: IRS Direct Pay, EFTPS, or Form 1040-ES voucher. State: usually state portal or mailed voucher.
Can I pay all at once at year-end?
Technically no: the penalty applies per quarter even if you pay all by Jan 15.
What about S-Corp owners?
S-Corp distributions are not subject to SE tax but are taxable as ordinary income. Plan quarterly to cover that.
Annualized income method?
For uneven income (consulting, capital gains), use Form 2210 Schedule AI to annualize.
One owner, one year, four payments.
A single-member LLC expects 120,000 dollars of profit this year. Last year's total tax was 28,000 dollars. The safe-harbor route: pay 100 percent of last year, so 7,000 dollars on each of the four dates, and the underpayment penalty cannot apply no matter how this year actually lands. If income arrived unevenly, the annualized method lets each payment track what was actually earned by that date, which suits seasonal businesses at the cost of more bookkeeping.
The penalty itself is modest but pointless: it accrues per quarter, like interest, on the shortfall between what was due and what was paid, and it applies even if you settle everything in April. That is the whole reason the calendar habit beats the year-end scramble: the same dollars, paid on four dates instead of one, cost strictly less. High earners note the 110 percent safe-harbor threshold, and states run parallel systems with their own dates, which your state guide carries.
Estimate once. Repeat quarterly.
Close enough beats not at all.
Size the payments with your real numbers, put the four dates on the calendar, and the penalty never meets you.
Deadlines verified against IRS instructions, July 2026. Service costs live in one place: pricing.