Overselling is expensive
Selling something you do not have costs you a refund, a disappointed customer, frequently a poor review, and marketplace penalties if it happens on a marketplace.
It happens because two channels sold the last unit within the sync interval, or because nobody decided which system was authoritative.
Pick the system of record
- Shopify as the master — simplest when Shopify is the main channel
- An inventory system as the master — right when you have warehousing complexity
- The ERP as the master — right when manufacturing or purchasing drives stock
There must be exactly one answer to “how many do we have?” Every other system reads it. Two systems both writing stock levels will diverge, always.
Sync frequency and buffers
Real-time sync is ideal and not always available. Where sync runs every few minutes, a buffer — holding back a unit or two from the marketplace — prevents most overselling.
- Shorter intervals for fast-moving lines
- Buffers on channels with penalties for cancellation
- Alerts when a sync fails, because silent failure means divergence
- A daily comparison report between systems
In-person sales are the usual gap
Trade counter sales, market stalls and phone orders are frequently recorded late or not at all, and they are the most common cause of a stock figure being wrong.
Whatever the process, it has to write to the same master as everything else, at the time of sale.
Reconcile physically
Systems drift from reality through breakage, theft, mis-picks and returns processed incorrectly. Cycle counting — checking a portion of lines regularly rather than everything annually — catches it early.
A store that has never physically counted its stock has an inventory system it should not fully trust.