For sellers doing $10K+/year on Whatnot, eBay, Mercari
Reseller bookkeeping
Live commerce and marketplace sellers face a bookkeeping problem none of the platforms solve: tracking what you paid for inventory. This guide covers what to record, how to categorize fees, and how it all maps to Schedule C. For Whatnot, eBay, Mercari, and TikTok Shop sellers.
Educational, not tax advice.
Resellers have unique tax situations (hobby vs business, casual vs full-time, multi-state nexus). Talk to a CPA who knows reseller tax. They exist and are worth the $300 to $800 a year.
What you paid: the whole game
Resellers buy low and sell high. The IRS only taxes the difference. So cost of goods sold (COGS) is your biggest deduction. Get it right and your tax bill is reasonable. Skip it and you pay tax on revenue, not profit.
Example: $50,000 in Whatnot sales for the year. You paid $30,000 for the inventory you sold. Your real taxable income is closer to $14,000 (after fees and shipping). Without cost records, you might file with $40,000+ as taxable. That's a $7,000+ overpayment at a 27% marginal rate.
Whatnot doesn't track what you paid.eBay doesn't. Mercari doesn't. None of them. It's on you.
What to record per item
| Field | Source | Why it matters |
|---|---|---|
| Purchase price | Receipt or lot invoice | Schedule C COGS |
| Acquisition date | Receipt | Inventory aging, holding period |
| Source | Where you bought it | Audit trail |
| Sold price | Platform CSV | Schedule C gross receipts |
| Sold date | Platform CSV | Year attribution |
| Platform fees | Platform CSV | Schedule C Line 27a |
| Shipping cost (paid by you) | Receipt or platform | Schedule C Line 27a or COGS |
| Grading cost (PSA, BGS) | Receipt | Add to COGS or Line 27a |
| Promo or Boost spend | Platform CSV | Schedule C Line 8 advertising |
Cost-tracking patterns that actually work
From talking to power sellers and Reddit polls. Here's what people use in the wild:
- Per-item entry at listing time. Most accurate. Highest friction. Works if you list slowly. Falls apart at 100+ items per week.
- Bulk-lot distribution. Bought a 50-card hobby box for $145. As you sell each card, distribute the $145 proportionally to sale price (or split equally). Math: card sells for $42, COGS is ($42 / total lot retail) × $145.
- Default rules by category. "Pokemon Crown Zenith ETBs always cost me $25 wholesale." Set once, applies to all matches. Less precise but covers volume.
- Receipt import. Pull eBay or Mercari purchase history (where you bought from). Match by date and title.
- Spreadsheet. 13 of 38 r/whatnotapp poll respondents do this. Works at small scale. Time sink at scale.
Multi-platform reconciliation
If you sell on Whatnot AND eBay AND Mercari, your year-end picture is fragmented across 3 different CSV formats with 3 different fee structures. The reconciliation pattern:
- Download all platforms' transaction CSVs for the year.
- Normalize to a common shape. Order ID, sold date, sold price, fees, shipping, buyer, costs.
- Tag each row by platform. Some items get listed across multiple platforms. Only count them once.
- Reconcile against each platform's 1099-K. Gross numbers should match.
- Sum into Schedule C line items.
This is what tools like CoinTracker do for crypto. One unified view across multiple sources, tax-ready exports. Resellers have been waiting for the equivalent. We're the Whatnot version of that. Multi-platform expansion is the v2 plan.
Fee categorization on Schedule C
| Fee | Schedule C line |
|---|---|
| Whatnot commission (8 to 10%) | Line 27a (Other expenses) |
| eBay final value fee (about 13%) | Line 27a |
| Mercari fee (about 10%) | Line 27a |
| Payment processing (Whatnot, eBay, Mercari) | Line 27a |
| Whatnot Boost or eBay promoted listings | Line 8 (Advertising) |
| Shipping (you paid) | Line 27a or part of COGS |
| PSA, BGS, SGC grading fees | Add to COGS or Line 27a |
| Card sleeves, top loaders, mailers | Line 22 (Supplies) |
| Mileage to post office or card shows | Line 9 (Vehicle) |
| Subscription tools (AfterShows, etc.) | Line 18 or Line 27a |
Hobby vs business: where the line is
The IRS distinguishes hobby sellers from business sellers. The categorization affects what you can deduct.
- Business. Profit motive, regular activity, run it like a business (records, separate bank account, intent to make money). Files Schedule C. Can deduct losses. Owes self-employment tax.
- Hobby. Casual, sporadic, not income-driven. Reports on Schedule 1 (Other income). Cannot deduct losses. No SE tax.
Most Whatnot sellers earning $5K+/yr are businesses by IRS definition. Don't self-classify as hobby just to skip paperwork. If audited, the IRS uses 9 factors to decide status.
Year-end checklist
- Pull all platform CSVs (Jan 1 to Dec 31).
- Reconcile gross against each 1099-K.
- Confirm every sale has a cost recorded. Fill gaps from your purchase records.
- Sum platform fees by category (Line 27a).
- Sum advertising and Boost spend (Line 8).
- Tally supply receipts (Line 22).
- Tally mileage (Line 9).
- Add subscription costs (Line 18 or 27a).
- Drop into TurboTax, FreeTaxUSA, or your CPA.
- Sanity check: does Net Profit (Line 31) feel right?
Year-round bookkeeping, automated
We read your Whatnot CSVs, track what you paid for each item with multiple entry patterns (manual, lot distribution, default rules), and give you a Schedule C-ready CSV when you need it. Multi-platform (eBay, Mercari) ships in v2. Pro is $19/mo. Usually pays for itself in 1 to 2 hours of saved bookkeeping.