A file arrives with item codes and quantities. Ask the provider whether it contains every balance or only changes since the last file. That answer determines what an absent item means.
Questions for the provider
Does quantity mean on hand or available to sell? Is it measured in items or packs? Does the file cover one location or several? These answers belong with the import configuration.
Reject incomplete input before applying it
For a full snapshot, check expected locations and required fields. A truncated export must not erase every balance omitted from the file. For a change file, establish how repeats and out-of-order deliveries are recognized.
Record the file identifier and the source measurement time. Import time may be much later than the stock count. If the next file never arrives, staff need to see that the balance has not refreshed.