📅 Quarterly Tax Calculator
Self-employed? The IRS wants pay-as-you-go. Estimate each quarterly 1040-ES payment and check the safe harbor.
How Quarterly Estimated Taxes Work
The US taxes income pay-as-you-go. Without an employer withholding for you, the IRS expects four estimated payments (Form 1040-ES) — miss them and you can owe an underpayment penalty even if you pay in full at filing time.
The Safe Harbor Rule
You avoid penalties by paying the lesser of: 90% of this year's tax, or 100% of last year's tax (110% if prior-year AGI exceeded $150,000). This calculator estimates your total tax (SE + income), computes both targets, and divides the smaller — minus what you have already paid — into four payments.
Worked Example
Single freelancer expecting $100,000 profit, prior-year tax $12,000, $8,000 already withheld. SE tax ≈ $14,130; income tax ≈ $12,060 → total ≈ $26,189. 90% of current = $23,570; safe harbor = 110% × $12,000 = $13,200. Pay the smaller: ($13,200 − $8,000) ÷ 4 = $1,300 per quarter — penalty-proof even though the true bill is higher.
Official reference: IRS.gov. This is an estimate for planning only — not tax advice. Verify with a CPA or tax professional before filing.
Safe Harbors That Eliminate Penalties
You can avoid underpayment penalties entirely with a safe harbor: pay 100% of last year's total tax (110% if AGI exceeded $150,000), or 90% of this year's tax, through withholding + timely estimates. For lumpy income (big Q4, seasonal business), the annualized income installment method (Form 2210 Schedule AI) lets you match payments to when income actually arrived instead of four equal chunks. Deadlines: April 15, June 15, September 15, January 15 — miss one and the penalty clock runs from that date even if you catch up later. Don't forget state estimated taxes, which have their own thresholds and are often where freelancers get blindsided. The federal penalty rate floats with interest rates (recently ~8% annually) — cheaper than credit cards, but an avoidable drag.
Frequently Asked Questions (FAQs)
When are quarterly taxes due?
Typically April 15, June 15, September 15, and January 15 of the following year. If a date falls on a weekend or holiday, the deadline shifts to the next business day.
What is the underpayment penalty?
The IRS charges interest (the federal rate, adjusted quarterly — recently around 8%) on the shortfall for the period it was unpaid. Safe-harbor payments avoid it entirely.
Who must pay quarterly estimated tax?
Generally anyone expecting to owe $1,000+ at filing after withholding and credits — freelancers, landlords, investors, and retirees with untaxed income.
What if my income is uneven?
You can use the annualized income installment method (Schedule AI) to match payments to when income was actually earned — useful for seasonal businesses.
Can I just increase W-2 withholding instead?
Yes. Withholding is treated as paid evenly all year even if increased in December — a legitimate year-end catch-up strategy if you also hold a W-2 job.
Last updated: September 2026
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Last updated: September 2026