Stock accuracy — counting without stopping
The two ways to count, how to read a variance, and the weekly habit that stops drift before it becomes a shortage.
Stock accuracy is the foundation everything else stands on: availability, purchasing, promised dates and job costs are all wrong the moment the numbers are. The good news is that keeping it true is a twenty-minute weekly habit, not an annual shutdown.
Part 01
How drift actually happens
2 minutes
Nobody loses 14 brackets at once. Someone takes two for a rush job on a Friday. A damaged one goes in the bin. Three go to a sample nobody raised paperwork for. Each is invisible, and each is permanent.
Drift is silent until a picker cannot fulfil a job. By then the cause is fifty small movements over two months and cannot be reconstructed — so you re-count, and start again from a known-good number.
Part 02
Two ways to count
2 minutes
| Type | What it is | When to use it |
|---|---|---|
| Real time | Count a handful of locations while the shop keeps running. The default, and the one you should live on. | Weekly, on your fastest-moving parts. Twenty minutes. |
| Complete | Count everything, as one exercise, with movement stopped. | Year-end, an audit, or restarting after drift has got away from you. |
An annual count finds an error up to twelve months after it happened, when nobody can explain it. A weekly count of ten fast-moving parts finds the same error within days, while someone still remembers the Friday rush job. That is why real time is the default.
Part 03
Reading a variance — a worked example
2 minutes
You count bay B-04 on a Friday. Three lines come back different. A stock take that finds discrepancies finishes in an issues state rather than simply completing — the variance is the point, not a footnote.
| Item | System | Counted | Variance | Likely cause |
|---|---|---|---|---|
| M8 bolts | 500 | 500 | 0 | Healthy. Most lines should look like this. |
| Steel blank | 120 | 106 | −14 | Material taken without a pick. The classic. |
| Bracket A | 40 | 46 | +6 | A works order completed but its material never issued, or a return not booked. |
Finding more than expected feels harmless and is not. It means a movement went unrecorded somewhere, so the same gap is producing wrong numbers elsewhere — often on the job that consumed the material. Investigate a plus the same way you would a minus.
Part 04
The habit that keeps it true
2 minutes
- Count ten fast-moving parts a week, not everything a year. Rotate through them. Twenty minutes buys you an early-warning system.
- Count the parts that move, not the parts that are valuable. A shelf of expensive castings that nobody touches will still be right in six months. The cheap fasteners everyone dips into will not.
- Fix the cause, not just the number. Adjusting the figure makes today right and next month wrong. Ask why the movement was not recorded — usually the answer is that recording it meant walking to a PC.
- Give it a name. Unowned counting does not happen, and this is the habit that quietly lapses first.
Most lines counting exactly right, a handful out by small amounts, and each of those explainable within a day or two. If every line is out, or none has been counted in months, the weekly habit is the fix — not a bigger annual count.