You sell the same necklace on Amazon, eBay and your Shopify store. You have one left. It sells on eBay at 2:10pm, and on Amazon at 2:12pm, before anything updated. Now you have to cancel an order, and that cancellation counts against you.
This is overselling, and it's one of the most common problems I see when brands start selling on more than one channel. The good news: it's very fixable with a simple system.
Why overselling hurts more than one sale
A cancelled order isn't just a lost sale. Marketplaces track how often sellers cancel, ship late or let customers down, and they use those numbers to decide how visible you are, and in bad cases whether you can keep selling. One or two mistakes won't sink you, but a habit of overselling slowly damages your account health on every channel.
1. Pick one source of truth for stock
Decide on one place where your real stock numbers live. For many brands that's Shopify; for others it's a dedicated inventory tool. Every other channel should take its numbers from there. Nobody should be typing stock counts into Amazon or eBay by hand.
2. Use the same SKU everywhere
A SKU is your internal code for a product. If your necklace is NK-GOLD-18 on Shopify, it should be exactly NK-GOLD-18 on Amazon and eBay too. Matching SKUs are what let your systems know these are the same item. Most syncing problems I fix start right here.
3. Connect every channel so stock updates automatically
Use an integration or multi-channel inventory app that connects your source of truth to each marketplace. When something sells anywhere, the stock drops everywhere. Before relying on it, check two things: how often it syncs (every few minutes is very different from once an hour) and what happens when a sync fails.
4. Keep a small safety buffer
Even good syncing has a delay. For fast-selling or low-stock items, show slightly less on your marketplaces than you really have, for example holding back the last one or two units. You might miss the occasional sale, but you avoid cancellations, which cost far more.
5. Treat Amazon FBA stock separately
If you use Fulfilment by Amazon, that stock sits in Amazon's warehouses, not on your shelf. Treat it as its own pool. If you want to sell it on other channels too, Amazon's Multi-Channel Fulfilment can ship those orders from the same stock. Just make sure your systems know which pool each sale comes from.
“The goal isn't perfect software. It's one set of numbers that everyone, and every channel, trusts.”
Your anti-overselling checklist
0 / 5 DONEThe short version
One source of truth, matching SKUs, automatic syncing, a small buffer, and a clear plan for FBA. Set that up once and overselling becomes rare instead of routine.
If you'd rather not set it up yourself, this is exactly the kind of thing I handle for the brands I work with. Book a free call and I'll take a look at your setup.
