Excess stock and inventory turnover: the cost of not knowing what is slow

01 / FIELD NOTE

Keep the decision tied to the operating context.

Excess stock is unusual among operational problems in that it costs money while appearing to be an asset. It sits on the balance sheet at cost, so the accounts show value; meanwhile it occupies space, consumes insurance and working capital, and loses value quietly. The loss only becomes visible at the point of markdown, by which time the decision that caused it is long past.

The cost has three parts and they arrive on different schedules. Capital is committed from the day the goods are received, which is a continuous cost. Storage and handling accrue throughout, which is a continuous cost. Obsolescence arrives in a step, when the season turns, the model is superseded or the shelf life expires, and it is the largest of the three. Only the first two give any warning.

Turnover measures how quickly stock is replaced, and it is the ratio that makes the problem legible: cost of goods sold divided by average inventory over a period, or its reciprocal expressed as days. A falling turnover means stock is sitting longer, whether because more was bought, less was sold, or the record has stopped reflecting either.

The difficulty is that an average conceals the distribution. A business can hold a healthy average while holding a large quantity of stock that has not moved in a year and a smaller quantity that turns constantly. The average is the sum of the two, and managing to the average means managing to a figure that describes neither.

Identifying the slow movers early is therefore the whole problem, and it requires two pieces of information that a periodic count does not produce reliably: the age of each item and its rate of movement. A count establishes what is present at a moment. Age and movement rate are properties of a history, and they need a record that has been maintained continuously rather than reconstructed at intervals.

Unit-level identity is what makes that history possible. If the record tracks quantities per product code, a receipt of stock is indistinguishable from stock already on the shelf, so first-in-first-out cannot be verified and the age of what is actually present cannot be established. If it tracks units, each receipt retains its own date and each item can be followed from receipt to sale or to the point where it stops moving.

The intervention window is what the visibility buys. A slow-moving item identified while it is still in season can be moved, transferred to a location where it sells, or promoted at a modest discount. The same item identified after the season has turned can only be cleared, and clearing is where the margin is lost. The difference between the two outcomes is not the decision but how early it was possible to make it.

Accuracy affects turnover through a less obvious route as well. When the record is unreliable, replenishment is ordered against a figure that includes stock the system believes exists. The business buys to cover an error and the error becomes physical stock, which is how a record problem turns into an excess inventory problem. The purchase order is where a counting failure finally becomes a financial one.

The mirror image is equally costly and easier to miss. Stock that is present but recorded as absent triggers a reorder that was not needed, and the arriving goods add to a position that was already sufficient. Both directions of record error push stock levels up, which is why an inaccurate record tends to produce excess rather than shortage over time.

Frequency of counting is what keeps age and movement information current. A record that is corrected twice a year cannot say when an item stopped moving, because the interval is longer than the phenomenon. A record maintained continuously, or counted frequently in pieces, can identify the point at which an item went quiet — which is the fact that makes an early intervention possible.

Where slow-moving stock accumulates across sites, the problem is usually a distribution one rather than a demand one. An item that does not sell in one location may sell in another, and moving it is far cheaper than marking it down. That reallocation requires knowing what is where across the whole estate, which is a visibility requirement rather than a forecasting one.

The honest position is that visibility does not reduce excess stock by itself. It makes the position legible early enough that a commercial decision can be made deliberately — move it, promote it, stop buying it — instead of being forced at the point where the only remaining option is to clear it at a loss. The saving comes from the timing of the decision, and the timing comes from the record.