Inactive stock: the dead weight on your storeroom shelves

Deep in the storeroom, behind the fast-moving shelves, sit rows of parts that have not moved since anyone can remember. Some were ordered for a machine that was replaced years ago. Others were bought in bulk and never fully used. They take up space, carry a book value, and quietly consume management attention.

Inactive stock identifies them. It is the metric that separates the living inventory from the slow accumulation of items that are almost certainly never coming back.

What it actually measures

Inactive stock is the percentage of non-critical MRO records that have had no usage in the past twelve months or more. Critical spares, held precisely because they are essential insurance against a serious failure, are excluded; the metric is about ordinary stock that ought to be moving and is not.

How to work it out

Inactive stock (%) = (Inactive records - critical spares × 100) / (Total records - critical spares)

A plant with 6,000 records, of which 1,200 are critical spares, finds 1,480 records unused for a year, but 1,140 of those are critical spares, leaving 340 genuinely inactive non-critical records.

Inactive stock = (340 × 100) / (6,000 - 1,200) = 7.1%

Those 340 items carry a book value of $230,000. Recovering even half of that through returns or disposal is a real contribution to working capital.

What good looks like

The best-in-class target is less than one per cent inactive stock, once critical spares are set aside, and it is worth knowing that this is an aggressive figure that assumes a mature, reliable operation. The wider context matters too: across maintenance storerooms, a large share of items, often half or more, go years without being touched, and most are infrequently used yet genuinely have to be on hand. The art is telling the legitimately dormant from the simply dead.

The instinct to cut, and why it is dangerous

There is a story that recurs across the industry, worth telling because the instinct it describes is so natural and so wrong. A stores manager, proud of his housekeeping, announces he will remove half the spare parts, since most have not moved in over a year. Senior management's response is blunt: doing that would be one of the worst things you could do. The reason is that a part sitting untouched for years is often not dead stock at all but insurance, the single spare for a critical machine, held precisely because the failure it guards against is rare and catastrophic. An item can also be inactive for the happiest of reasons, because the plant is so well maintained that the failure never came. Strip those parts out to tidy a metric and you have not freed cash, you have removed the plant's protection against its worst days. This is a number to act on with a scalpel, never a shovel.

Where it can mislead you

• Define critical spares with a consistent, documented process. Over-classifying items as critical will artificially deflate the inactive figure and hide the problem; under-classifying will put genuine insurance spares at risk of being cut.
• Before disposing of anything, run a risk assessment. Some items are inactive precisely because the plant is well maintained, and removing them could open a gap.
• Inactive does not automatically mean obsolete. Confirm the item still has a valid application before writing it off.
• Trend it over time. A rising inactive percentage is a sign your purchasing or stocking decisions are getting ahead of what the plant actually consumes.

Inactive stock puts a number on the dead weight in your storeroom, and a target for clearing it. Handled with a little care, so that genuine insurance spares are protected, it is one of the cleaner opportunities maintenance has to hand cash back to the business, but only if the cutting is done with judgement rather than a blanket rule.