How to manage inventory when selling on several marketplaces
To manage inventory across several marketplaces without selling stock you no longer have, you need a single balance per SKU: one central number that is decremented by a sale on any channel and automatically updates all the others. Spreadsheets and native panels cannot do this in real time — which is why multichannel operations use an ERP or hub integrated via API.
Why does inventory drift between channels?
When the same product is listed on Mercado Livre, Shopee and Magalu, each marketplace keeps its own stock counter. A sale on Mercado Livre does not notify Shopee. Unless you update manually — and fast — the other channels keep selling an item that has already left the shelf.
- Simultaneous sale of the same last unit on two channels: one of the orders gets cancelled.
- Cancellations hurt your marketplace reputation (and reputation drives visibility and the buy box).
- Manual updates always arrive late: the gap between the sale and the spreadsheet is the error window.
The 4 possible approaches (and where each breaks)
| Approach | How it works | Where it breaks |
|---|---|---|
| Spreadsheet | You log stock in/out and update each channel by hand | Not real time; human error; does not scale past a few sales a day |
| Native panels | Manage stock inside each marketplace separately | No unified view; the same product becomes N independent counters |
| Integration hub | Syncs stock between channels via API | Solves sync, but usually not invoicing, finance or dispatch |
| Integrated ERP | Single balance per SKU + orders, invoicing and dispatch in one flow | Requires migrating the catalogue once — the cost is initial setup |
How the single balance per SKU works
In the single-balance model, stock lives in the central system — not in the marketplaces. Every listing points to a catalogue SKU. When a sale comes in on any channel, the system decrements the central balance and propagates the new number to every other listing via API.
- A sale comes in on Shopee: the order is imported automatically.
- The system decrements the SKU balance and reserves the unit for the order.
- The new balance is published to Mercado Livre, Magalu and the other channels.
- If the balance hits zero, listings pause automatically — nobody buys what does not exist.
In Facilwork this propagation runs in cycles of up to 60 seconds, through each marketplace’s official API.
The special case of kits and bundles
A kit is a listing that sells several SKUs together ("3-pack", "gift set"). Kit stock does not physically exist: it is derived from its components. The right calculation is virtual stock — the smallest number of kits you can assemble with current balances.
Example: a kit uses 2 units of SKU A and 1 of SKU B. With 10 of A and 3 of B in stock, the kit’s virtual stock is 3 (limited by B). Sell one kit and the components are decremented, and every other kit using A or B is recalculated instantly. Doing this in a spreadsheet with dozens of kits is unworkable — an operation like Yespack keeps 446 kits with automatically calculated virtual stock.
Best practices to avoid overselling
- One SKU per physical product, always — each colour/size variation is its own SKU.
- Reserve the unit at sale time, not at dispatch.
- Set minimum-stock alerts per SKU to restock before hitting zero.
- Listings on different channels must point to the same SKU, never to copies.
- Run periodic stock counts: the right system makes adjustments easy, with an audit trail of who changed what.
Frequently asked questions
What happens if two marketplaces sell the last unit at the same time?
With a single balance and immediate reservation, the first imported sale reserves the unit and the new balance (zero) pauses the other listings. The conflict window drops to seconds — versus hours with manual control.
Do I need to re-create my catalogue on each marketplace?
No. In Facilwork you map the listings you already have on each channel to the SKUs in the central catalogue. Stock becomes centrally managed without recreating listings.
Does kit virtual stock work with shared components?
Yes — that is the point. If two kits use the same component SKU, selling one instantly recalculates the other’s virtual stock.