How to sync inventory across Amazon, eBay & Shopify without overselling
Overselling quietly wrecks your marketplace metrics and your margins. Here is the exact real-time setup that keeps every channel accurate.
Why overselling happens in the first place
Most overselling is not a stock problem, it is a timing problem. When each marketplace holds its own copy of your inventory, every manual edit and delayed webhook opens a window where two buyers can grab the last unit.
The more channels you add, the wider that window gets. A sale on TikTok Shop at 2pm does not reach eBay until your next export, and by then the cancelled order and the dinged metric are already done.
The moment your stock lives in one place, overselling stops being a fire you fight every week.
Set a single source of truth
Pick one master catalog and make every channel read from it. In Commercium your available quantity is calculated centrally and pushed outward, so no marketplace ever holds a number you did not sanction.
Add a small safety buffer on fast movers. Reserving two or three units absorbs the seconds between a sale and the next sync, cheap insurance against a cancellation.
Automate the sync, then trust it
Turn on real-time sync and let it run. When a unit sells anywhere, Commercium deducts it everywhere within seconds, and low-stock rules can pause a listing before it ever oversells.
The goal is not to watch dashboards all day, it is to stop watching them. Once the numbers reconcile themselves, inventory becomes a weekly review, not an hourly fire drill.
Put this into practice
Connect 200+ marketplaces with one no-code connector and keep every channel in sync.