Estimated tax calculator for the self-employed
Drop your 2026 income and expenses. Quartersafe works out self-employment and income tax, the safe harbor, and what to pay each quarter — in your browser, nothing uploaded.
How much to pay each quarter
From Form 1040-ES: if you expect to owe $1,000 or more after withholding, you pay estimated tax in four installments — April 15, June 15 and September 15, 2026 and January 15, 2027. Each installment is normally a quarter of the required annual payment: the smaller of 90% of your 2026 tax or 100% of your 2025 tax (110% if your 2025 AGI was over $150,000).
A worked example
The app's sample: a freelance designer with $57,801.10 of net profit through October, projected to $72,004.78 for 2026. Estimated 2026 federal tax is $14,804.47; last year's tax was $9,800 (AGI $82,000), so the safe-harbor target is $9,800.00 — 100% of last year's tax, less than 90% of this year's ($13,324.02). Two $2,450 payments were made in April and June; September was missed.
| Installment | Regular (25% each) | Annualized (Schedule AI) | Paid |
|---|---|---|---|
| Q1 | $2,450.00 | $849.65 | $2,450.00 |
| Q2 | $2,450.00 | $1,610.28 | $2,450.00 |
| Q3 | $2,450.00 | $3,289.48 | $0.00 |
| Q4 | $2,450.00 | $4,050.59 | $0.00 |
The annualized method lowers the September requirement, so the shortfall since September 15 is smaller. Either way, $4,900.00 by January 15, 2027 reaches the safe harbor.
What you get
- Your 2026 federal tax estimate: self-employment tax, the half-SE and 20% QBI deductions, income tax on the 2026 brackets and Additional Medicare.
- The safe harbor: the smaller of 90% of this year's tax or 100%/110% of last year's.
- Each required installment by the regular method and by the annualized method (Form 2210 Schedule AI), with the cheaper one picked.
- What to pay by January 15, 2027, and the balance due with your return.
- Checks: a 2025 payment counted for 2026, a missed installment, duplicates, transfers and other-year rows.
Files it reads
A CSV or Excel file with a date and an amount on each row — a bank or card export, a Stripe or PayPal activity report, or an export from your bookkeeping app. Positive amounts are income, negative are expenses, or use separate income and expense columns. IRS payments (USATAXPYMT, Direct Pay, EFTPS, 1040-ES) are counted as estimated payments; rows categorized as transfers, draws or personal are left out.
Your numbers stay on your computer
Quartersafe reads your file with JavaScript in this browser tab. Income, clients and expenses are never uploaded, and closing the tab clears them.
How it works
- Drop your 2026 income and expenses (CSV or Excel) — or try the sample, or download the template.
- Enter last year's tax and AGI from your 2025 Form 1040, plus any W-2 wages and withholding.
- Read the January 15 number and the checks, then pay through IRS Direct Pay or EFTPS. With Pro, keep the full Schedule AI worksheet for Form 2210.
FAQ
What does Quartersafe do?
It reads your 2026 business income and expenses, works out your 2026 federal tax (self-employment tax and income tax), the safe-harbor amount that avoids an underpayment penalty, and the required installment for each quarter under both the regular method and the annualized income installment method (Form 2210 Schedule AI). Then it subtracts what you've paid and shows what to pay by January 15, 2027. It doesn't pay or file anything.
Is my data uploaded?
No. Your file is read by JavaScript in your browser tab and never sent to us or anyone else. Transactions aren't stored, so closing the tab clears them. Settings can be saved in this browser.
What's the safe harbor?
From Form 1040-ES and the Form 2210 instructions: you generally won't owe an underpayment penalty if, on time each quarter, you pay at least the smaller of 90% of your 2026 tax or 100% of the tax on your 2025 return — 110% if your 2025 adjusted gross income was over $150,000 ($75,000 if married filing separately). You also owe no penalty if your 2026 tax minus withholding is under $1,000.
When are 2026 estimated payments due?
April 15, June 15 and September 15, 2026, and January 15, 2027. You can skip the January payment if you file your 2026 return and pay all the tax due by February 1, 2027.
What is the annualized income installment method?
If your income was uneven — say a slow spring and a busy fall — you can work out each required installment from the income you'd actually earned by the end of each period (March 31, May 31, August 31, December 31) using Form 2210 Schedule AI. That can lower or remove the penalty for the early quarters. Quartersafe runs it for you and compares it with the regular 25%-a-quarter method.
Which files can I use?
CSV, tab-separated or Excel with a date and an amount on each row — positive for income, negative for expenses — or separate income and expense columns. A description and category are optional and help spot IRS payments and transfers. Download the template to see the layout.
What's free?
Importing any number of rows, the tax estimate, the safe harbor, both methods' installments, what to pay by January 15, and every check, plus the first Schedule AI period line by line on screen and in print (with a footer). Pro shows and prints the full Schedule AI worksheet without the footer and exports the Excel workbook, a Schedule AI CSV and the categorized transactions CSV.
What isn't covered?
State estimated tax, capital gains and qualified dividend rates, tax credits, itemized deductions, other taxes such as the net investment income tax, the qualifying-surviving-spouse status (use married filing jointly, which shares its tables), and farmers' and fishermen's rules. The QBI deduction is left out above the income threshold where its limits begin.
Is this tax advice?
No. Quartersafe applies Form 1040-ES and Form 2210 (with Schedule AI) to the data you provide. Ask your tax adviser what applies to you.