What Is an Inventory Control System?

What Is an Inventory Control System?

An inventory control system is the set of procedures and tools that lets a business know, at any moment, what goods and materials it owns, where they are, what they are worth and when it needs to order more. It is not just software that counts what is in the warehouse. It is a process that starts when goods are ordered from a supplier, runs through receiving, storage, transfers and issues, and ends at sale or consumption, with every movement and its financial effect recorded along the way.

Businesses without clear inventory control face the same problems again and again: book balances that do not match the shelves, sudden shortages of important items, goods nobody can find, and an annual count that reveals variances no one can explain. Each of these means buying and pricing decisions are being made on wrong numbers.

This guide explains the two types of inventory control system, the components any good system needs, how inventory is valued with a worked example, the journal entries behind stock movements, the internal controls that prevent loss, a comparison of manual and automated control, and practical steps to put a system in place.

The Two Types of Inventory Control System

Perpetual inventory

In a perpetual system, every item's balance updates the moment something happens. A receipt increases it, a sale or issue reduces it, and a transfer moves it from one location to another. Cost of goods sold is recorded with each sale, so the income statement is available on any day without waiting for a count.

This suits businesses with many items, several locations or high daily volume, and it is how most modern ERP systems work. It does not remove the need for physical counts. System balances drift from reality through damage, theft and data entry errors, and regular counting is how that drift is found and corrected.

Periodic inventory

In a periodic system, balances do not update with each movement. Purchases go to a purchases account, a physical count is taken at the end of the period, monthly or yearly, and cost of goods sold is worked out as: opening inventory + purchases minus closing inventory.

A hypothetical example: a shop starts the year with SAR 200,000 of stock, buys SAR 900,000 during the year and counts SAR 250,000 at year end. Cost of goods sold = 200,000 + 900,000 minus 250,000 = SAR 850,000. The problem is that this figure includes shrinkage and damage with no distinction, so you cannot tell how much was sold and how much was lost.

Periodic inventory suits very small businesses with few items and slow movement. As the business grows, it becomes a handicap, because management sees real balances only once a period.

Core Components of an Inventory Control System

1. Clean item master data

Everything starts with the item record: a unique code, a clear name, a base unit of measure plus alternate units such as carton and piece, a category, a reorder level, a main supplier, and a tracking method if the item needs batch or serial numbers. Messy master data, such as duplicate items under different names, corrupts every report that follows.

2. Every movement backed by a document

The golden rule is no movement without a document. Receipts use a goods receipt linked to the purchase order, issues use an issue note or invoice, transfers use a transfer document with a sent and received status, and adjustments use an approved adjustment that states the reason. A movement without a document is, by definition, unexplained loss.

3. Defined storage locations

Knowing an item is somewhere in the warehouse is not enough. In larger warehouses each item needs a specific location by aisle, rack and level, which speeds picking, simplifies counting and cuts search time. Remember the non-physical locations too: goods in transit between branches, rejected goods awaiting return to the supplier, and stock held at a customer site for display. Each needs its own location in the system so it is not counted as available to sell.

4. Reorder management

A minimum level for each item at each location, an alert when it is reached and a suggested order quantity. Just as important, review those levels regularly, because a level that was right a year ago may now be causing stockouts or surplus.

5. Inventory classification

ABC analysis ranks items by annual consumption value, so the most valuable items get tighter control and more frequent counts. We walk through the method in our guide to ABC analysis.

6. Batch and serial tracking

For food, medicines, cosmetics and chemicals, you need to know every batch and its expiry date, so that the earliest-expiring stock goes out first and affected quantities can be found quickly in a recall. In pharmaceuticals, for example, the Saudi Food and Drug Authority requires medicines to carry a 2D barcode with batch number, expiry date and serial number under the national drug track and trace system. For equipment and devices, serial numbers make warranty and service tracking possible for each unit. More in our article on batch tracking.

7. Barcodes and automated capture

Scanning barcodes at receiving, issuing and counting cuts manual entry errors and speeds up every transaction. RFID can read many units without pointing a scanner at each one, but costs more and suits specific cases such as high-value items or returnable containers.

8. Reporting

The reports every inventory manager needs: balances by location, items below reorder level, slow movers, turnover by category, count variances, items nearing expiry, and the movement history of any single item.

Inventory Valuation: What Is Your Stock Worth?

Inventory control is not only about quantities. You also need the value in the books. IAS 2, applied in Saudi Arabia under IFRS as endorsed by SOCPA, allows two main cost formulas for interchangeable items: first in, first out (FIFO) and weighted average. LIFO is not permitted. Inventory must also be measured at the lower of cost and net realisable value.

A hypothetical example for one item over a month:

• Opening balance: 100 units at SAR 50.
• Mid-month purchase: 200 units at SAR 56.
• Sales during the month: 220 units.

The weighted average here is (5,000 + 11,200) / 300 = SAR 54. The difference is only SAR 160 in this example, but it multiplies across thousands of items and volatile prices. What matters is choosing one method, applying it consistently and letting the system calculate it with every movement.

The Journal Entries Behind Stock Movements

In a perpetual system, every stock movement carries an accounting entry. Using the weighted average example above:

• Purchase: debit inventory SAR 11,200 and input VAT SAR 1,680; credit the supplier SAR 12,880.
• Sale: two entries. Revenue: debit the customer, credit sales and output VAT. Cost: debit cost of goods sold SAR 11,880, credit inventory SAR 11,880.
• Count shortage: if 76 units are found instead of 80, the shortage is 4 x 54 = SAR 216: debit inventory shortage expense, credit inventory.
• Write-down: if net realisable value falls below cost: debit inventory write-down expense, credit the inventory valuation allowance.

When inventory and accounting share one system, these entries are generated automatically with each document, and the inventory account in the general ledger always agrees with the stock valuation report. When they are separate, that reconciliation becomes a tiring monthly task that rarely ends without a difference.

Common Causes of Variances and How to Fix Them

A hypothetical illustration of the money involved: a warehouse holding SAR 5 million of stock with 1.5% unexplained annual shrinkage loses SAR 75,000 a year. Halving that rate with the controls above saves SAR 37,500 a year, plus less time chasing variances and buying decisions built on correct balances.

Internal Controls That Prevent Loss

A good system does not just record; it prevents errors and abuse before they happen:

• Segregation of duties. The person who requests a purchase does not receive it, the receiver does not approve the supplier invoice, and the custodian of stock does not perform the count.
• Defined permissions. Storekeepers can post receipts and issues, but adjustments need a manager's approval.
• Three-way match. Purchase order, goods receipt and supplier invoice must agree before payment.
• Two-step transfers. Transferred goods sit in an in-transit location until the receiving site confirms arrival.
• Surprise counts. Counting selected items without notice surfaces problems quickly.
• Audit trail. Every change to balances or master data is logged with the user and time.

Physical Counting: Part of Control, Not a Substitute

Even with the best system, physical counts remain necessary. The choice is not between one annual count and none, but between approaches:

• Full annual count. Stops operations for a day or more, usually at financial year end. In Saudi Arabia the Commercial Books Law requires year-end inventory to be recorded in the inventory book. Note that the new Commercial Transactions Law approved by the Council of Ministers in October 2026 will replace the Commercial Books Law 180 days after publication, so check the updated requirements with your adviser.
• Cycle counting. Counting part of the range each week so every item is covered within a set period, with A items counted more often.
• Event-triggered counts. Counting an item when its balance hits zero or when an issue reveals a discrepancy.

For practical guidance on planning and running counts, see our guide to stocktaking.

Inventory accuracy rate

The single most important measure of an inventory control system is balance accuracy: the number of items whose physical count matched the book balance within an accepted tolerance, divided by the number of items counted. Count 400 items, match 368, and accuracy is 92%. If accuracy is low, sophisticated reorder calculations are wasted, because they start from a wrong balance.

Manual vs Automated Inventory Control

Spreadsheets can work for a small business with a few dozen items and one site. The real cost of manual control shows up in undetected shrinkage, urgent orders and staff time spent reconciling, none of which is visible to someone looking only at the software price.

Choosing the Right Inventory Control System

1. Integration. Does it connect to purchasing, sales and accounting, or does data have to be exported and imported?
2. Multiple sites and units. Does it support several warehouses and branches, and different units for the same item?
3. Tracking. Does it handle batches, expiry dates and serial numbers if your business needs them?
4. Warehouse usability. Can a storekeeper use it quickly, and does it support barcodes?
5. Reporting. Can you build the reports you need without a developer every time?
6. Compliance. Are sales invoices issued from the system compliant with ZATCA e-invoicing requirements?

Implementation Steps

1. Clean the master data. Standardise codes, names and units; remove duplicates and unused items.
2. Define locations. Code warehouses, aisles and racks before loading data.
3. Write the procedures. Who receives, who approves, how returns and damage are handled, which documents transfers require.
4. Take an opening count. Start from physical balances, not from the old system's numbers.
5. Train by role. Storekeepers, buyers and accountants need different training.
6. Start cycle counts in month one, so procedural gaps show up early.
7. Review metrics monthly: accuracy, turnover, slow movers and stockouts.

How Tranquil Supports Inventory Control

Tranquil's inventory management module covers central inventory, multiple units of measure, pre-assemblies and assembly, and connects to purchasing, sales and financial accounting in one cloud system, with customisable screens, reports and multi-level approvals. For manufacturers, barcode integration is available within the manufacturing solutions. Contact the Tranquil team to review what your warehouse needs.

Frequently Asked Questions

What is the difference between inventory control and inventory management?

Inventory management is the broader discipline covering planning, forecasting, buying and storage. Inventory control is the part focused on accurate balances, recorded movements and the controls that prevent loss and error.

Do I still need physical counts with a perpetual system?

Yes. The system only knows about movements that were entered. It cannot see damage, theft or unrecorded errors. Regular physical counts are what find and correct those differences.

Should I use FIFO or weighted average?

Both are acceptable under IAS 2. FIFO mirrors the physical flow of dated goods, while weighted average is simpler for homogeneous, fast-moving items. Consistency matters more than the choice.

How often should A items be counted?

There is no mandatory frequency, but a common practice is monthly for A items, quarterly for B items and once or twice a year for C items. Adjust based on results: an item with recurring variances deserves more frequent counts.

When do I need batch tracking?

When you handle items with expiry dates, items under regulatory traceability rules such as medicines, or items you may need to recall. In those cases batch tracking is a requirement, not an option.