Quarterly estimated taxes in Excel

If clients do not withhold federal income tax, you may owe quarterly estimates. Excel will not file Form 1040-ES for you — but a clean invoice, expense, and mileage workbook makes the inputs honest. This is a practical checklist, not tax, legal, or accounting advice.

2026 due-date rhythm (typical)

Period covered	Typical due
Jan 1 – Mar 31	April 15 (or next business day)
Apr 1 – May 31	June 15
Jun 1 – Aug 31	September 15
Sep 1 – Dec 31	January 15 of following year

Weekends and holidays shift the exact day. Confirm on the IRS estimated tax calendar before you pay.

What to total in Excel before you estimate

Cash received — invoices paid in the period, not just invoices sent
Ordinary expenses — software, supplies, contractors, home office if eligible, with receipts
Business miles — date-aware log (2026 rates change mid-year: 72.5¢ then 76¢)
Prior-year tax — for safe-harbor checks (often 100% / 110% of last year’s tax — confirm current rules)
State estimates — if your state requires them, track separately

Where spreadsheets beat guesswork

One workbook can hold billed amounts, paid amounts, and Schedule C–style categories
A planned-vs-actual budget shows whether a strong quarter will spike your estimate
A free mileage log with the July 1, 2026 rate split keeps car deductions from being a sticky note

Full tax software or a preparer still owns the final calculation. Your job is not inventing numbers the week before the due date.

Quick pre-payment checklist

Filter the expense sheet to the quarter’s dates
Sum paid invoice amounts (or deposits) for the same window
Export or print mileage rows that fall in-period
Pay via IRS Direct Pay / EFTPS / 1040-ES voucher; save confirmation numbers

Yellow = your numbers. Gray = formulas. No macros. No monthly fee for the templates themselves.