Every reseller should track six things: what each item cost, where and when you bought it, what it sold for and when, the fees the platform took, the shipping you paid, and your business expenses. Get those down consistently and you can always answer the two questions that matter — how much did I really make? and what do I owe come tax time? — without a weekend of digging.

This applies to any kind of reselling: sneakers, trading cards, clothing, electronics, collectibles, or a mix. The categories change; the records you keep don't.

1. Order details (the cost side)

For every item you buy to resell, capture:

What it is — a title you'll recognise later
Cost — what you actually paid
Date bought and retailer/source — where it came from
Quantity — if you bought multiples

This is your cost basis. Without it, every later profit number is a guess.

2. Sale details (the revenue side)

When it sells, record:

Sell price and date sold
Platform — which marketplace
Status — listed, sold, returned, etc.

The date-sold matters more than people expect: it's how you separate this month's performance from last month's, and how you place income in the right tax period.

3. Fees (per platform, per sale)

Every marketplace takes a cut, and they differ — eBay's final value fee isn't Vinted's isn't Depop's isn't Whatnot's. Record the fee per sale, not as a flat average, or your profit will be systematically wrong. If you sell across several platforms, this is the single most common place margins get overstated.

4. Shipping

Track what postage actually cost you on each order, including any delivery you absorbed to offer "free shipping." A heavy item can quietly turn a profitable sale into a break-even one.

5. Expenses

These don't attach to a single sale but still come out of your profit — and in most places, they're deductible. Common reseller expenses:

Packaging and shipping supplies
Mileage / travel to source stock or post items
Subscriptions and software
Storage or shelving
Marketplace or listing costs
A share of phone / internet if used for the business

Logging expenses as you go is what turns a vague "I think I made a few grand" into a defensible figure.

6. Profit (the number that ties it together)

Real profit is:

profit = sell price − item cost − fees − shipping − expenses

If you've tracked items 1–5, this falls out automatically. It's also the figure that should match your bank — if it doesn't, one of the inputs is missing.

A quick word on tax

General information, not tax or financial advice. Tax rules for reselling vary by country and change over time — for example, some regions have a small "trading allowance" or hobby-vs-business thresholds, and online marketplaces increasingly report seller activity to tax authorities. What counts as a deductible expense also varies. Check your local tax authority or a qualified accountant for your specific situation.

What's universal is this: good records make tax painless. If your orders, fees, expenses and profit are already logged cleanly, you (or your accountant) can produce whatever's needed in minutes instead of reconstructing a year from memory.

Make it a habit, not a chore

The reason most resellers don't keep these records isn't that they don't know they should — it's that doing it in a spreadsheet is tedious and easy to skip. A tool built for reselling removes the friction: you log an order, and the fees, profit and totals are handled for you.

That's what Reseller OS does. It's a desktop app — your data stays on your machine, no account, no cloud — and you set it up with your own platforms, retailers, categories and currency. Orders, expenses, income and real profit, all in one place.

Launching in beta. Join the waitlist — free through the beta, with a spot in the Discord.

Track these six things consistently and your reselling stops being a shoebox of guesses and starts being a business you can actually read.