Inventory reporting: stock turns and aging

Inventory reporting answers two questions that are often confused. Stock turns measure how many times the stock balance was sold and replaced during a period. Aging measures how long the stock currently on hand has been sitting there. A business can post healthy turns overall while holding a large block of stock that has not moved for a year, which is why the two reports belong on the same page.

Stock turns measure flow and aging is a snapshot. Use turns to judge whether the buying plan matches demand, and use aging to decide what to do with stock already owned. Neither report is a valuation exercise, but both must reconcile to the inventory ledger before anyone acts on them.

Stock turns = cost of goods sold / average inventory at cost. Average inventory is normally (opening + closing) / 2, though a monthly average is better when the balance swings through the year. Inventory days = average inventory / cost of goods sold x 365, which is the same measure expressed in time rather than frequency.

A distributor with cost of goods sold of 1,200,000 and average inventory at cost of 200,000 has 6 turns and about 61 inventory days. Valuing the same stock at retail, say 300,000, would produce 4 turns and understate performance. The error is common when the stock system reports retail value and the accounts report cost, and it makes comparison between categories unreliable.

A company-wide turns figure is an average, and averages hide the problem. Split turns by category, supplier, or warehouse and compare each group with its own demand pattern. Consumables should turn far more often than spare parts held for a long service obligation, and a single target across both is meaningless.

Item-level turns are noisy because one large order can distort a month. Use a rolling twelve-month cost of goods sold at item level, then review only the items outside their category range. That keeps the list short and the analysis stable.

Age each stock line from its last movement date, not its original purchase date. A line replenished last week is not old stock because the first receipt was two years ago. Where the system only keeps receipt dates, use first-in-first-out layers and say so in the report notes.

Bucket value into 0 to 30, 31 to 60, 61 to 90, 91 to 180, and over 180 days, and show units, cost value, and share of total value for each bucket. A large unit count in the oldest bucket matters less than a small count with high value.

A report listing every stock line gets ignored. Write rules that produce a short list each month, and attach an owner and a decision date to every item on it.

The decision is usually one of four: sell at a discount, return to the supplier, write down, or hold with a stated reason and a review date. Recording the reason matters as much as the decision, because it stops the same item returning to the list every month.

A useful monthly page shows total inventory value, turns, days, the aging profile, and the exception list. Add a short bridge explaining the change in value since last month: purchases, cost of sales, write-offs, and revaluations. If the bridge does not close, the stock ledger and the report are using different data.

Review the page with the people who buy stock, not only with finance. Turns and aging are buying decisions before they are accounting ones.