A business with several branches usually knows how much stock each holds, on paper. Whether that number is accurate enough to tell a customer 'yes, we have it' is a different question, and the gap between the two is where the commercial value sits.
The first decision is what the system is for. Visibility — seeing where stock is — is comparatively easy. Commitment — promising a unit to a customer and reserving it — requires the numbers to be right in near real time, and that is a much stronger requirement on every process that touches stock.
Reservation logic is where designs get complicated. When an online order is placed, which branch's stock is committed? For how long, if the customer has not paid? What happens when a walk-in customer at that branch takes the same unit off the shelf five minutes later? These are business rules and they need business answers, not defaults.
Cycle counting keeps the numbers honest. A full annual stock take finds the discrepancies once a year, by which time the causes are untraceable. Counting a small rotating subset continuously finds them while the transactions are recent enough to investigate, and it is far less disruptive.
Transfers between branches are the most common source of drift. Stock leaves one location and arrives at another, and in the interval it belongs to neither in the system, or to both. Modelling in-transit as an explicit state with its own ownership prevents an entire category of unexplained variance.
Set an accuracy target and measure against it before promising availability to customers. A business that publishes live stock levels at eighty per cent accuracy generates cancellations, refunds and lost trust — outcomes worse than not publishing at all.
