What do you owe by the next quarterly deadline?
Nobody can forecast a freelance year accurately, and the good news is that you do not have to. The safe harbour rules let you pay a fixed amount based on last year and be immune to the underpayment penalty regardless of how this year turns out. This works out which rule is cheaper for you, and what to pay when.
Example: $120,000 expected profit, single filer, no prior-year return
The form for your own figures loads with JavaScript, and checks today’s date against the deadlines.
Pay $25,616 across the year, in four instalments
That is $6,404 per period for a full year of payments. The live calculator checks today’s date and moves anything you can no longer pay on time onto the periods still open.
The four payment periods
| Income earned | Due | Amount |
|---|---|---|
| Q1January 1, 2026 – March 31, 2026 | April 15, 2026 | $6,404 |
| Q2April 1, 2026 – May 31, 2026 | June 15, 2026 | $6,404 |
| Q3June 1, 2026 – August 31, 2026 | September 15, 2026 | $6,404 |
| Q4September 1, 2026 – December 31, 2026 | January 15, 2027 | $6,404 |
This example assumes a full year ahead of you. Deadlines that have already passed cannot take a payment, and the calculator accounts for that once it loads.
Projected tax for the year
- Self-employment tax
- $16,955
- Federal income tax
- $11,506
- Total
- $28,462
Which safe harbour applies
Paying 90% of this year’s expected tax is the smaller requirement, so that is the target. With a prior-year return you would also have the option of paying 100% of last year’s tax, which is safer when income is rising because it does not depend on forecasting this year correctly.
Federal only — most states run their own estimated payment schedule. Method and sources are on the methodology page; these are estimates, not tax advice.
The three safe harbours
You avoid the underpayment penalty if any one of these is true. Only one has to be.
- You owe less than $1,000 after withholding and credits.
- You paid at least 90% of this year’s tax.
- You paid at least 100% of last year’s tax — 110% if last year’s AGI was over $150,000.
The third is the one worth understanding. It depends on a number you already know exactly — last year’s tax — rather than a forecast. If your income doubles this year, paying last year’s figure still protects you from the penalty. You will owe the difference in April, but no penalty on top.
The 2026 deadlines
The periods are uneven, which surprises people. Q2 covers two months, Q4 covers four.
- Q1 — income from January 1, 2026 to March 31, 2026, due April 15, 2026
- Q2 — income from April 1, 2026 to May 31, 2026, due June 15, 2026
- Q3 — income from June 1, 2026 to August 31, 2026, due September 15, 2026
- Q4 — income from September 1, 2026 to December 31, 2026, due January 15, 2027
A deadline falling on a weekend or federal holiday moves to the next business day. None of the 2026 dates do.
Missed one?
Pay as soon as you can rather than waiting for the next deadline. The underpayment penalty is calculated like interest, per day, on what was unpaid — so paying late costs less than paying later, and far less than not paying. It is not a flat fine, and being a few weeks late on one quarter is usually a small amount of money.
What this planner leaves out
- State estimated payments. Most states run their own schedule, with their own thresholds and sometimes different dates.
- The annualised income method. If your income is heavily seasonal you may owe less early in the year than an even split implies. That is Form 2210 Schedule AI, and it needs quarter-by-quarter figures this planner does not ask for.
- Credits and other income. Anything beyond business profit, other ordinary income and withholding.
Method and sources are on the methodology page. Estimates for planning, not tax advice — see the disclaimer.