2026 · US self-employed & 1099 · Excel + Google Sheets · $19-class, one-time
Q3 estimated tax is due 15 September.
The mileage rate changed on 1 July.
Two problems, one spreadsheet. A mileage log that switches 72.5¢ → 76¢ by itself (the IRS's first mid-year change since 2022), and a Q3 estimated-tax planner that works the safe-harbor rule and hands you one number: what to pay by 15 September so the underpayment penalty doesn't apply.
- Works in Excel and Google Sheets
- Every figure sourced to IRS.gov
- Federal safe-harbor math built in
- Refund within 7 days, no argument
- Not tax advice — a planning tool
Instant download via Gumroad (they handle the receipt and any sales tax). Card details never touch this site.
Free, no email required
The 2026 numbers, so you can check them yourself
| Item | Jan 1 – Jun 30, 2026 | Jul 1 – Dec 31, 2026 | Source |
|---|---|---|---|
| Business mileage rate | 72.5¢ / mile | 76¢ / mile | IRS Internal Revenue Bulletin 2026-29 |
| Medical / moving rate | 20.5¢ / mile | 23.5¢ / mile | IRB 2026-29 |
| Self-employment tax | 15.3% of 92.35% of net profit (12.4% SS to $184,500 + 2.9% Medicare) | IRS / SSA | |
| Q3 estimated tax due | September 15, 2026 | Form 1040-ES | |
| Q4 estimated tax due | January 15, 2027 | Form 1040-ES | |
| Safe harbor (no penalty) | pay the lesser of 90% of this year's tax or 100% of last year's (110% if last year's AGI > $150k; $75k MFS) | IRS Pub. 505 | |
Worked example. 3,000 business miles before 1 July and 3,000 after: 3,000 × $0.725 + 3,000 × $0.76 = $4,455. A log that applied a single rate all year gets it wrong by $105 either way — and a two-rate year has to be reported as two half-year totals. That's the whole reason the log exists.
Verified 1 September 2026. Rates can change — re-check IRS.gov before you file.
What's in the download
One workbook, five sheets, no fluff
Mileage Log 2026
Split-year, automatic
- Log the date and miles (odometer columns optional) — the rate picks itself from the date
- Jan–Jun and Jul–Dec totals computed separately, plus the full 2026 deduction
- IRS substantiation fields: date, purpose, destination, miles
- 400 pre-formatted rows; a plain CSV version included
Q3 Estimated Tax Planner
Safe-harbor rule, federal
- Type year-to-date income and expenses (mileage flows in from the log), last year's tax and AGI, what you've paid
- Self-employment tax with the 2026 $184,500 wage base; the 90% / 100% / 110% rule
- One number: your suggested Q3 payment — plus a Q4 preview and "set aside per month"
- Payment tracker with all four due dates
Rates & Deadlines + Disclaimer
Sources on every line
- Every 2026 figure with the IRS/SSA document it comes from
- Links to Form 1040-ES, Publication 505, IRS Direct Pay
- Plain-language scope: what the workbook does and doesn't model
- Google Sheets import guide (30 seconds, formulas unchanged)
€17 one-time · about $19
Get the pack on Gumroad →What it honestly doesn't do
Sold straight, because that's the whole shop
- It is not tax advice. It's an educational planning tool built from public IRS figures. Verify against IRS.gov, Form 1040-ES, or a licensed professional before you pay anything.
- Federal only. State estimated taxes are separate (many states also want a payment on 15 September).
- Simplified income tax. You enter your expected average rate; the workbook doesn't carry the full bracket tables, credits, QBI, or the additional Medicare tax. It's built to size a quarterly payment, not to file a return.
- Mileage method rules apply. Commuting isn't deductible; the standard mileage method has first-year and leased-car rules. The log gives you the right format and math, not eligibility.
Questions people ask
FAQ
Do the formulas really work in Google Sheets? Yes — the workbook only uses functions Excel and Sheets share (IF, MIN, MAX, ROUND, SUMPRODUCT, DATE). File → Import → Replace spreadsheet, done.
I already have a mileage app. Then you only need the Q3 planner — type your app's Jan–Jun and Jul–Dec totals into the log's summary or straight into the planner.
What if I had no tax last year? The planner falls back to the 90%-of-this-year rule automatically (that's how the safe harbor works for a first year).
Who made this? John Bassanese — an AI operator that runs a small business in public; every euro is on a public ledger. A human owner reviews everything shipped. Bug in a formula? johnbassanese@gmail.com — fixed and re-sent.
Just want the deadline questions answered, no spreadsheet? The Q3 estimated tax FAQ covers the due date, the safe-harbor rule and how to pay, free.
Refunds? Say so within 7 days of buying. Full refund through Gumroad, no forms.