Split your 2026 tax bill into four on-time payments, with the safe harbor that fits
Use expected profit for the whole year (revenue minus business expenses), not just what you've earned so far. The estimate is federal only: 2026 brackets, the $16,100 / $32,200 standard deduction, and SE tax. It leaves out QBI, credits, and state tax.
| Payment | Covers Earnings From | Due Date |
|---|---|---|
| Q1 | January 1 – March 31 | April 15, 2026 |
| Q2 | April 1 – May 31 | June 15, 2026 |
| Q3 | June 1 – August 31 | September 15, 2026 |
| Q4 | September 1 – December 31 | January 15, 2027 |
If a date falls on a weekend or federal holiday, it moves to the next business day. Notice the quarters aren't equal: Q2 covers only two months of earnings, which is why June's payment often feels oversized. Individuals pay free at IRS.gov/payments (Direct Pay) or by mail with a 1040-ES voucher; businesses generally use EFTPS.
| Rule | Requirement | Best For |
|---|---|---|
| 90% of current year | Pay 90% of what you'll actually owe for 2026 | Incomes that dropped this year |
| 100% of prior year | Pay exactly last year's total tax, in 4 installments | Incomes that rose; prior-year AGI ≤ $150,000 |
| 110% of prior year | Prior-year AGI above $150,000 ($75k MFS) | High earners with rising income |
| Withholding shortcut | Boost W-4 withholding to cover side income | W-2 + 1099 hybrid earners |
The safe harbor is an either/or: meet one and there's no underpayment penalty even if you end up owing more in April. The catch is that the safe harbor only prevents penalties, not the tax itself, so whatever remains is still due at filing.
Quarterly estimated taxes are pay-as-you-go withholding for people without an employer. The IRS expects four payments a year, and it penalizes you, quarter by quarter, for coming in under the safe harbor. This calculator builds your full-year federal bill first, then splits it into payments and checks both safe harbors.
SE tax: net profit × 0.9235, then 12.4% up to the $184,500 wage base and 2.9% Medicare on everything (plus 0.9% above $200k single / $250k joint). Income tax: wages plus profit, minus half the SE tax, minus the standard deduction ($16,100 single / $32,200 joint), run through the 2026 brackets. Total tax ÷ 4 is the even-payment plan; the safe-harbor column shows the prior-year alternative.
Enter your expected profit for the full year, any W-2 wages and withholding, and last year's tax and AGI. The calculator recommends the smaller of the two safe-harbor payments and flags which rule you're using. If your income is seasonal or lumpy, you can use the annualized income method on Form 2210 to pay less in slow quarters, but that's Schedule AI territory; most people just pay evenly.
A single freelance developer expects $90,000 of net profit for 2026, with no W-2 job, and paid $18,000 of total tax last year. SE tax: 90,000 × 0.9235 = $83,115 of net earnings, $10,306 Social Security + $2,410 Medicare = $12,717. Income tax: AGI is 90,000 − 6,358 (half of SE tax) = $83,642, minus the $16,100 standard deduction leaves $67,542 taxable, which runs through the 10%, 12%, and 22% brackets to $9,571. Total: $22,288.
Ninety percent of that is $20,059, or $5,015 a quarter. But the prior-year safe harbor says $18,000 ÷ 4 = $4,500 a quarter (prior AGI was under $150,000, so 100% applies). The smaller check wins: pay $4,500 per quarter, on time, and there's no penalty even though April will bring a bill for the remaining $4,288. That final lump sum is the trade-off the safe harbor offers, smaller quarterly checks, same total tax.
April 15, June 15, and September 15, 2026, then January 15, 2027 for the fourth payment. Each payment covers a different earning period: Jan 1 to Mar 31, Apr 1 to May 31, Jun 1 to Aug 31, and Sep 1 to Dec 31. When a date lands on a weekend or holiday it slides to the next business day.
Divide 90% of your expected current-year tax into four payments, or pay 100% of last year's tax (110% if your prior-year AGI was over $150,000), whichever produces the smaller checks. A single freelancer expecting $90,000 of net profit owes roughly $22,288 total for 2026, which is $5,015 a quarter at the 90% target, but only $4,500 a quarter under the prior-year safe harbor if last year's tax was $18,000.
You must make estimated payments if you expect to owe $1,000 or more at tax time beyond what's withheld. That threshold catches most full-time freelancers and many side-gig earners. You're off the hook if you had zero tax liability last year (as a US citizen or resident for 12 months), or if withholding already covers 90% of this year's bill.
The IRS charges an underpayment penalty, calculated per quarter at a floating interest rate (recently 7% to 8% annually) that compounds daily. It isn't a fine with a fixed price tag; it's interest on the shortfall for the days it was late. Paying late in the year but before April still triggers the penalty for the gap months.
Yes, and it's underrated. If you have a W-2 job, filing a new W-4 with extra withholding can cover your side income, because withholding is treated as paid evenly across the year no matter when it was actually taken out. That forgives late quarters that estimated payments never would.
Yes. Estimated payments cover your total federal bill: income tax plus SE tax minus any withholding or refundable credits. For most freelancers the SE tax half is the bigger half, which is why a $90,000 profit generates about $12,717 of SE tax and only about $9,571 of income tax.