Overselling
What is overselling?
Overselling is taking an order for stock that is no longer there — the shop accepts and confirms a purchase for an item the warehouse has already sold. It happens when the quantity on the site lags behind the quantity in the warehouse, or when the same item is sold on several channels at once. The result is a cancelled order, a refund, and a customer who will not wait twice.
Example
A clothing shop sells through its own site and two marketplaces. Stock is refreshed once a day, overnight. It takes 1,500 orders a month, and 1.8% of them are cancelled for want of stock — 27 orders. At an average of €55 that is around €1,485 of turnover that does not happen, plus the refund fee and roughly 15 minutes of work per case.
Two changes move the number. The exchange goes from once a day to several times a day, and an order reserves the quantity at checkout rather than at dispatch. Items down to fewer than two pieces are shown as “last few”. Cancellations fall to 0.4%, or 6 orders: about €1,155 of turnover recovered each month. The amounts are illustrative, but the mechanism is exactly that — a shorter interval and an earlier reservation.
Why it matters for a business
Overselling is expensive for what follows rather than for the single order. Marketplaces watch the share of seller-cancelled orders and answer with worse placement or restrictions. On your own site the cost is trust: a customer who paid and then got an apologetic call rarely comes back, and the review stays up to be read.
The cause is almost never a bad system; it is the interval. The link between warehouse and shop runs on a schedule and travels through a file or an API, and between two exchanges the shop sells against the last quantity it was told. So the fixes are a buffer per item, a reservation at checkout, a shorter cycle for fast movers, and a rule about which channel wins when one piece is left.
Those rules are set during warehouse sync and tested against the real numbers of the shop rather than left at their defaults.
How to improve it
- Shorten the interval between exchanges for the items that sell fastest.
- Reserve the quantity at checkout, not at dispatch.
- Hold a buffer on items that are sold on more than one channel.
- Stop selling at zero instead of accepting orders to ship later.
- Track the share of cancelled orders every month — that is the number that says whether the rules work.