This is for United States FEDERAL tax, tax year 2026, and nothing else. A seller in Canada, the UK or the EU should stop reading here, and so should anyone filing for 2025. It says so in the product name, on the workbook title, on the first line of the first sheet, in a red banner across the top of all twelve sheets, and against every constant on the Sources sheet. It does not compute state or city tax and it does not model any state 1099-K threshold. Being unmistakably one thing is the point.

Here is the moment this product exists for. It is late January, a Form 1099-K lands, and box 1a says $48,000. You know perfectly well you did not make $48,000 — you cleared something under ten thousand — but you cannot prove it line by line, and the number on the form is the number the IRS already has. That gap is the single most common panic in reselling, and it has a boring, provable explanation: the IRS instructions say box 1a is reported "without regard to any adjustments for credits, cash equivalents, discount amounts, fees, refunded amounts, shipping amounts, or any other amounts." Your final value fees are inside it. Your refunds are inside it. The postage your buyer paid you is inside it. The form was never your income and was never meant to be.

So the flagship sheet walks the whole chain, per platform, and ties out: box 1a gross → refunds and cancellations → platform and final value fees → payment processing → shipping labels → other statement adjustments → net payout → cost of goods sold → mileage and every other expense → home office → Schedule C line 31. On the sample data that ships in the file, $48,000 of box 1a becomes $9,706.57 of actual profit, and the workbook shows every line in between. Print that page and staple it to your 1099-K; if anyone ever asks how one became the other, the answer is on it.

Nothing on the reconciliation sheet is estimated from a fee percentage, and that is deliberate. Fee schedules change several times a year and differ by category and by shipping label; while this file was being built, two aggregator sites disagreed about eBay's rate and eBay's own page said something different from both of them. A rate you typed in last March is a guess. Your statement is a fact. So the reconciliation uses only the figures you copy off your own statements, and fee rates appear nowhere near your tax figures.

The second half is the one nobody builds: inventory. Cost of goods sold is not what you spent on stock this year — it is what the items that actually SOLD cost you, and every item carries its own cost by specific identification. The workbook does the whole of Schedule C Part III from a plain item log: beginning inventory, purchases, items withdrawn for personal use, ending inventory, line 42. It also puts the number that hurts on the Dashboard: money you spent on stock that has not sold yet, and how much of that you bought in November and December. That is cash gone with no deduction until it sells, and knowing it in October is worth considerably more than $19.

Personal things stay out. Selling your own old coat for less than you paid is not a business loss and never was — IRC 165(c) disallows it — and selling it for more is a capital gain. Tick one box and the workbook keeps those rows off Schedule C entirely and reports them separately, which is exactly what a preparer needs and what almost every reseller template gets wrong.

Then the tax, with no "enter your tax rate %" cell anywhere — there is no such cell in this file and there never will be. Schedule SE lines 3 to 13 with the 92.35% adjustment and the 12.4% Social Security part capped at the $184,500 wage base for 2026. Form 8959 for the 0.9% Additional Medicare Tax. The 2026 rate schedules for all five filing statuses. The section 199A deduction on Form 8995-A, including the $400 minimum that applies for the first time in 2026. All three safe-harbour tests, which one binds, and the four estimated-tax due dates. Every rate is read off the Sources sheet, where it is printed with the IRS or SSA document it came from, the URL and the day it was checked.

One of those checks matters more than the rest. The IRS raised the business mileage rate mid-year: 72.5 cents to 30 June 2026 under Notice 2026-10, then 76 cents from 1 July under Announcement 2026-11. Almost every reseller spreadsheet on the market still carries one rate for the whole year and quietly loses you the difference. The Mileage Log here totals your miles separately either side of 1 July and applies both rates.

You can check every number, and we checked them for you. Behind the workbook is an independent Python model of the 2026 tax — the same one that powers our $29 tax engine, imported rather than retyped — and the build asserts twelve seller scenarios cell by cell against it: 2,568 comparisons to the cent, plus a full LibreOffice recalculation with zero formula errors both as shipped and with every input cleared. Twelve live reconciliations sit at the foot of the Schedule C Map sheet so you can see the file agreeing with itself. Where something could not be verified, the Sources sheet says so plainly: Poshmark's fee page could not be read when this file was built, so its preset row ships BLANK with the URL to read, rather than carrying a number nobody checked.

It ships filled in with a fictional three-platform reseller — $48,000 of box 1a across eBay, Poshmark and Mercari, 218 items logged, $3,720 of stock still unsold — so every sheet is alive the moment you open it. Clear the yellow cells and it is yours. Classic formulas only, so it behaves identically in Excel 2016 and later, Excel 365, Excel for Mac and Google Sheets. A six-page print pack comes with it in US Letter and A4, colour and ink saver.