---
url: https://thresholds.pages.dev/estimated-taxes/
title: "Estimated tax calculator (Form 1040-ES): what to pay and when"
updated: 2026-09-07
site: Thresholds
sources:
  - https://www.irs.gov/forms-pubs/about-form-1040-es
  - https://www.irs.gov/publications/p505
  - https://www.irs.gov/forms-pubs/about-form-2210
---

# Estimated tax calculator (Form 1040-ES): what to pay and when

The two federal safe harbors, the four installments, what is already short at a date that has passed, and the January waiver.

The federal underpayment penalty of IRC §6654 does not apply if your withholding plus timely installments cover the SMALLER of two targets: 90% of this year's total tax, or 100% of last year's total tax — 110% of last year's total tax when prior-year adjusted gross income was over $150,000 ($75,000 if married filing separately). Neither figure is indexed; both have stood since 1993.

Two rules the arithmetic turns on. The prior-year safe harbor needs a full 12-month prior tax year and a filed return — so a first-year freelancer has no prior-year harbor at all and only the current-year test applies. And Withholding counts as paid in equal parts on each installment date, which is why raising W-2 withholding late in the year is the one move that reaches backwards and cures an earlier shortfall.

There is no penalty at all when the balance due after withholding and credits is under $1,000 (IRC §6654(e)(1)).

## Tax year 2026 installments

| Installment | Income earned | Statutory date | Due | Moved? |
|---|---|---|---|---|
| Q1 | Jan 1, 2026 – Mar 31, 2026 | Apr 15, 2026 | Wednesday, April 15, 2026 | no |
| Q2 | Apr 1, 2026 – May 31, 2026 | Jun 15, 2026 | Monday, June 15, 2026 | no |
| Q3 | Jun 1, 2026 – Aug 31, 2026 | Sep 15, 2026 | Tuesday, September 15, 2026 | no |
| Q4 | Sep 1, 2026 – Dec 31, 2026 | Jan 15, 2027 | Friday, January 15, 2027 | no |
| Waiver | file and pay in full instead of installment 4 | Jan 31, 2027 | Monday, February 1, 2027 | yes — January 31 is not a business day |

The calculator at https://thresholds.pages.dev/estimated-taxes/ takes filing status, prior-year total tax and AGI, whether a full 12-month prior return was filed, expected current-year tax and expected withholding, and what has already been paid in each quarter. It returns both harbors with the binding one named, the required annual payment, the per-quarter amount, the record of payments with cumulative credit, the shortfall at each date, and the annualized income installment method of Form 2210, Schedule AI for uneven income.

It does not compute a dollar penalty: that needs the IRC §6621 underpayment rate, and Resets quarterly — check the current IRS rate. Federal only. Nothing typed is uploaded.

## Sources

- [IRS — About Form 1040-ES](https://www.irs.gov/forms-pubs/about-form-1040-es)
- [IRC §6654(d)(1)(B)(i); IRS Pub 505; Form 2210](https://www.irs.gov/publications/p505)
- [IRS Form 2210](https://www.irs.gov/forms-pubs/about-form-2210)

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Information, not advice. Figures verified 2026-09-07. https://thresholds.pages.dev/estimated-taxes/