Slow stock is a loan you give your products: what a month on the shelf costs

Stock that sits on the shelf is not neutral. Every month it stays there, someone pays to hold it, and in most owner-managed businesses that someone is you. The price list does not show it, and the P&L rarely shows it by product.

The problem: holding cost is invisible by product

Most accounts show stock as one balance sheet number, and interest as one line in the P&L. Nothing connects the two to a specific product. A fast mover and a slow mover with the same gross margin look identical, yet the slow one has tied up cash for months longer.

That is why slow stock behaves like a loan you give your own products. They borrow your money, you charge them nothing, and the margin you thought you earned is quietly smaller.

Why it matters now

The Bank of England held Bank Rate at 3.75% in September 2026, with the next decision due on 5 November. It also notes that energy prices are volatile and that inflation is expected to rise further from its current level. Money is not cheap, and it is not getting cheaper in the short term.

Input costs add to the pressure. The Office for National Statistics reported that producer input prices rose 6.1% in the year to August 2026, while factory gate prices rose 3.7%. When materials cost more, each pound sitting in stock is a larger pound than it was a year ago. The next ONS release is due on 21 October 2026, so check whether the gap has narrowed or widened before you act on the numbers below.

The solution: put a financing charge on every slow SKU

The method is simple. For each product group, multiply the stock value by your cost of money and by the share of the year it sits.

For illustration only: £40,000 of one product held for 180 days at 3.75% costs about £740 in financing (£40,000 × 0.0375 × 180 ÷ 365). If your own borrowing or overdraft rate is higher than Bank Rate, which is common, use that rate instead. Add storage, handling and the risk of write-off, and the true cost of the shelf month becomes visible. These figures are illustrative; use your own stock report.

Compare that charge with the gross profit the product earned over the same period. Where the charge takes a large share of the profit, the product is not paying its way.

Tips and tricks for this week

1. Export your stock report and list the ten SKUs with the longest time on the shelf.
2. For each, calculate stock value × your actual cost of money × days held ÷ 365.
3. Add an allowance for storage, handling and the chance of write-off.
4. Decide per SKU: reduce the order quantity, raise the price, or stop stocking it.
5. Set a minimum order quantity based on how fast each product actually sells, not on the supplier's price break alone.

Why the principle holds

Both sources point the same way. The Bank of England explains that Bank Rate influences the cost of borrowing across the economy, and ONS data shows input prices still outpacing selling prices. Charging products for the capital they use is the same logic applied inside your own business. If you want a structured view of where margin leaks, the Business Health Check is a starting point.