Alerting on stock
A list of low items is not an alert. A decision with a date is.
Rank by days of cover, not by units
Units remaining divided by recent daily rate, then compared with the supplier's lead time. Forty units with a fourteen-day lead time and a six-a-day rate is urgent; four hundred of something that sells once a week is not.
Three buckets
Order today — cover is below lead time. Order this week — cover is below lead time plus safety. Watch — trending toward the line.
Say what to order
Quantity, based on the rate and the lead time, and the minimum order quantity if there is one. An alert that leaves the buyer to do the arithmetic gets deferred.
Flag separately
Anything with a promotion or a seasonal peak inside the lead-time window, where the recent rate is the wrong basis.
Never
Alert on every low item, or use a fixed unit threshold across products that sell at completely different rates.