# Quarterly estimated tax calculator

> Your four 2026 federal estimated tax payments and their due dates, figured two ways: the safe harbor that avoids the underpayment penalty, and the projected tax. Free, and it runs in your browser.

Canonical: https://usetruenote.com/tools/quarterly-estimated-tax

A free calculator at https://usetruenote.com/tools/quarterly-estimated-tax. It runs in the browser (JavaScript); nothing typed is sent anywhere. The math is Truenote's own federal tax projection (`packages/domain`), the same one the app runs on a household's real figures.

## Inputs

- Filing status
- Net self-employment income: expected profit for the year, after business expenses
- W-2 wages: for the year, after 401(k) and other pre-tax deductions (box 1)
- Federal tax withheld: from W-2 pay, for the whole year
- Last year's tax (Form 1040 line 24) and last year's AGI (line 11): optional, for the safe harbor
- Children under 17 at the end of the year: the child tax credit
- State: Texas and the other states without an income tax say so; elsewhere the result is federal only

## Output

For each of the four periods (Q1 January–March, Q2 April–May, Q3 June–August, Q4 September–December), its due date and two amounts:

- **Safe harbor:** a quarter of what avoids the underpayment penalty, beyond withholding: the smaller of 90% of this year's tax or 100% of last year's (110% when last year's AGI was over $150,000, $75,000 married filing separately). Owing under $1,000 after withholding needs no estimated payments.
- **Projected:** a quarter of the projected tax beyond withholding, so nothing is left to settle in April.

Both round up to the dollar. Below them: the statement line by line (total income, less half of self-employment tax, adjusted gross income, the standard deduction, the qualified business income deduction, taxable income, income tax, the child tax credit, self-employment tax, total tax, withholding, projected amount owed), what it assumes and what it leaves out.

## 2026 due dates

April 15, 2026; June 15, 2026; September 15, 2026; January 15, 2027. A weekend due date moves to the Monday after.

## How it's figured

Self-employment tax is 15.3% of 92.35% of net profit (12.4% Social Security up to the $184,500 wage base less W-2 wages, 2.9% Medicare); half of it comes off income. Then the standard deduction, the qualified business income deduction (20%, with the phase-in), income tax by bracket, the child tax credit ($2,200 a child), the additional Medicare tax. 2026 figures: IRS Rev. Proc. 2025-32 and the SSA's 2026 wage base.

It leaves out: state income tax, credits other than the child tax credit, the alternative minimum tax, investment income and capital gains, itemized deductions, self-employed health insurance and retirement contributions, the annualized-income method.

## Questions

**Do I have to pay quarterly if I also have a W-2 job?** Maybe not. Withholding counts toward the safe harbor and is treated as paid evenly through the year, so raising W-2 withholding can replace quarterly payments.

**Does Texas have a state income tax?** No. A Texan's estimated payments are federal only.

**Is this tax advice?** No. It's an estimate from the figures entered. Check anything that matters with a tax professional.

Related: [How much to set aside for taxes when you're self-employed](https://usetruenote.com/guides/self-employed-tax-set-aside.md). With Truenote connected, an agent gets the same projection from a household's real figures through the `get_tax_projection` MCP tool.