A retailer's stock system shows a number for every style in every store. That number is called the book stock. It is not a guess. It is built from every receipt, every sale and every transfer the system has recorded for that location. But the book stock is only as good as the events that fed it, and in a real store many of those events are recorded late, recorded wrong, or never recorded at all. A carton arrives and is put straight on the shelf before anyone scans it in. A till goes offline for an hour and a clerk rings the sale on paper. Each of these small gaps pushes the book stock a little further from the truth.
This lesson gives you the habit of treating book stock as a claim, not a fact, and physical stock count as the check on that claim. You will learn what a book stock is, why it drifts from reality even in a well-run store, and how to read the gap between the two counts as useful information rather than a simple mistake to blame on someone.
You need: a basic understanding of a purchase order, a shop, and how a stock system records a sale. No previous lesson in this course is needed.
By the end of this lesson you can:
Not covered here: how to run a cycle count (Lesson 3.2), sorting a variance into theft, damage or administrative error (Lesson 3.3), or costing what inaccuracy takes off an order's margin (Lesson 3.4). This lesson only teaches why the two counts differ.
| Term | Meaning |
|---|---|
| Book stock | The quantity a stock system shows for a location, built up from every receipt, sale and transfer it has recorded. |
| Physical stock count | Counting the real units sitting on the shelf or in the stockroom by hand, to check against the book stock. |
| Perpetual inventory system | A stock system that updates its book stock automatically after every recorded receipt, sale and transfer, rather than only at a yearly count. |
| Point of sale (POS) | The till system that records a sale and reduces book stock at the moment a customer pays. |
| Inventory accuracy rate | The physical count divided by the book stock, shown as a percentage, measuring how closely the system matches reality. |
| Stock discrepancy | The difference between what the book stock claims and what the physical count actually finds. |
Fairway Stores runs a perpetual inventory system. Every receipt from Northline Apparel, every sale at the point of sale, and every transfer between stores changes the book stock the moment it is entered. That design is a real strength: staff can check a book stock figure at any time without stopping to count. The weakness sits in the word "recorded." The system only knows about events someone told it about, in the way they told it. A carton put on the shelf before it is scanned in, a sale rung under the wrong size, or a transfer logged a day late all leave the book stock believing something that is no longer true.
| What can differ | The shapes you meet | Why it matters to you |
|---|---|---|
| Business model | A Make to Stock chain like Cedar & Co. holds stock across many shops and a long selling season, giving many small events time to drift the book stock. A Make to Order export shipment, once landed, has fewer events before it sells through, so the book stock usually stays closer to reality for longer. | The longer stock sits and the more it moves between locations, the more chances the book stock has to drift from the real count. |
| Market | An export brand's own shops, like Northline Apparel's shops, and a domestic chain, like Fairway Stores or Cedar & Co., both run perpetual systems, but a domestic chain with more, smaller stores usually has more receiving and transfer events per unit sold. | More locations and more transfers mean more places for an unrecorded or wrongly recorded event to happen. |
| How the stock is received | Stock scanned in unit by unit at receiving gives the system an accurate starting book stock. Stock put onto the shelf before it is scanned, common under time pressure, starts the book stock wrong from day one. | An error made at receiving affects every later count of that batch until it is caught. |
| How the stock is sold | A single item scanned at the point of sale reduces book stock cleanly. A multi-pack, a promotional bundle, or a till working offline can record the wrong quantity or the wrong style. | The point of sale is the main place book stock is reduced, so an error there directly creates a discrepancy. |
| Product family | A fast-moving basic style like Order A's T-shirt sells in high volume with frequent size and colour mix-ups at the till. A slower, higher-value style, or a set with several pieces such as a bedding set, has fewer transactions but a bigger cost per error. | Both a high-volume basic and a low-volume higher-value style need book-stock checking, but the reason a gap matters differs. |
Fairway Stores buys Order A's T-shirt from Northline Apparel wholesale and sells it through its own department stores. At Store 4, the stock system's book stock for the T-shirt, size M, shows 1,200 units. A routine physical count of the same size on the same shelf and stockroom finds 1,140 units.
Nothing in the system flagged a problem before the count. The book stock simply carried forward every receipt and sale it had been told about, and none of those records showed an error. The gap only became visible once someone counted the real shelf and compared it with the number the system was showing.
The worked numberA 95% accuracy rate means the book stock overstates the real shelf by 60 units, or 5% of what the system claims to hold. On its own, that single number does not say why the 60 units are missing. It says only that the book stock can no longer be trusted at face value for this style at this store until the gap is explained, which is exactly what the next two lessons in this course teach.
A stock system does not warn anyone when it is wrong. It only reports what it was told, so a book stock can sit untouched and apparently confident for months while the real shelf drifts further away from it. Treating an unflagged book stock as proof of accuracy, rather than as an unchecked claim, means a store can build reorder decisions, size-run analysis and even markdown timing on a number that no longer matches reality. The cost of that mistake is not the 60 missing units themselves; it is every later decision made as if those 60 units were still there to sell.
A stock system's number is built from everything it was told about a shelf, not from looking at the shelf itself. Every receipt, every sale and every transfer feeds that number, and if any one of those events is late, wrong or missing, the number drifts a little from the truth. A physical count is simply looking at the real shelf and counting what is actually there. When the two numbers disagree, that gap is not proof of a mistake by any one person. It is a signal telling you where to look before you trust the system's number again.
Fairway Stores' book stock for Order A's T-shirt, size M, at Store 4 shows 1,200 units. A physical count this week finds 1,140 units. A replenishment order from Fairway Stores' own head office is due to be placed against the book stock figure in two days.
Should the store manager let the replenishment order go out using the book stock figure of 1,200 units? Decide before opening the answer.
No. The store manager should correct the book stock to the physical count of 1,140 units before the replenishment order is calculated, and open a check into the cause.
1. The gap of 5% is above the store's own 3% tolerance, so it does not qualify as ordinary, expected drift. 2. A replenishment order calculated from the wrong book stock would understate real need by 60 units, because the system would believe more stock is already on the shelf than actually exists. 3. Correcting the book stock first, then reordering from the corrected figure, protects the store from running out of size M before the cause of the 60-unit gap is found.
The store manager does not need to know yet whether the 60 units are theft, damage or an administrative error. That question belongs to Lesson 3.3. The immediate decision only needs the size of the gap against the tolerance, and the fact that an order is about to be placed on a number that has already been shown to be wrong.
Order A's T-shirt has an agreed FOB of USD 3.20 per piece and a shop price of USD 19.90 (docs/02 section 7). If Store 4's replenishment order is placed against the wrong book stock of 1,200 units instead of the corrected 1,140, the store risks running short by 60 units before the next delivery arrives.
That figure is not a claim that USD 1,194 is definitely lost; a customer who cannot find size M may buy a different size instead, or come back later. It shows the scale of what one uncorrected 60-unit gap can put at risk at a single store, for a single size, in a single style, which is why the cost of inaccuracy is treated fully in Lesson 3.4 rather than guessed here.
Use the T21-C03 Inventory accuracy and shrinkage tracker workbook, "Book vs physical count" sheet. For each store or stockroom you check, record the style, the book stock, the physical count, the count date, and let the sheet calculate the variance and the inventory accuracy rate. Start with the Fairway Stores Store 4 example above, then add one location of your own.
[Download the Inventory accuracy and shrinkage tracker workbook](../../templates/T21-C03-inventory-accuracy-shrinkage-tracker.xlsx)
Download the Inventory accuracy and shrinkage tracker (Excel)
1. Why can a perpetual inventory system's book stock still be wrong even though it updates automatically after every event?
2. Fairway Stores' Store 4 shows a book stock of 1,200 units and a physical count of 1,140 units for Order A's T-shirt, size M. What is the inventory accuracy rate?
3. A different store shows a book stock of 800 units and a physical count of 792 units. What is the accuracy rate, and is it as urgent as Store 4's 95% result?
| EN | AR | FR | TR | Meaning |
|---|---|---|---|---|
| Book stock | الرصيد الدفتري | Stock théorique | Kayıtlı stok | The quantity a stock system shows for a location, built up from every receipt, sale and transfer it has recorded. |
| Physical stock count | الجرد الفعلي | Comptage physique | Fiziksel sayım | Counting the real units sitting on the shelf or in the stockroom by hand, to check against the book stock. |
| Perpetual inventory system | نظام الجرد المستمر | Système d'inventaire permanent | Sürekli envanter sistemi | A stock system that updates its book stock automatically after every recorded receipt, sale and transfer, rather than only at a yearly count. |
| Point of sale (POS) | نقطة البيع | Point de vente (POS) | Satış noktası (POS) | The till system that records a sale and reduces book stock at the moment a customer pays. |
| Inventory accuracy rate | معدل دقة المخزون | Taux de précision du stock | Envanter doğruluk oranı | The physical count divided by the book stock, shown as a percentage, measuring how closely the system matches reality. |
| Stock discrepancy | الفرق في المخزون | Écart de stock | Stok farkı | The difference between what the book stock claims and what the physical count actually finds. |
Next you will learn how to run a rotating cycle count so an inventory error is caught within days instead of being found once a year. Back to the course map