A shop can be busy, profitable on paper and quietly losing margin on its best sellers, all at the same time. It happens whenever costs move faster than prices.
The loss nobody sees
You buy cooking oil at one rate and set a selling price. Two months later the supplier rate has moved twice and the selling price has not. Every sale is still recorded as a sale, and nothing anywhere says the margin has gone.
It only becomes visible at the end of the year, as a profit figure lower than the turnover suggested it should be.
Keep the purchase history
The fix is unglamorous: record what you paid, every time, per item. Then the last five purchase rates for any item are one look away.
That single view answers two questions at once. Is this supplier's offer actually good, and is my selling price still above what the stock now costs to replace.
- Record the rate on every delivery
- Compare against the last few purchases, not the first
- Check the fast movers most often
Price on replacement cost
The relevant cost is not what the stock on your shelf cost you. It is what the next delivery will cost. If you price on the old figure you are funding your customers' inflation out of your own margin.
This matters most on the items that turn over fastest, which are usually the ones with the thinnest margins already.
Review on a schedule
Once a month, look at the top thirty items by volume and check the current cost against the current price. Half an hour, and it is the highest-return half hour in the shop.
Doing it reactively, when something feels wrong, means doing it too late.
You cannot control what suppliers charge. You can control whether you notice.
