Inventory Management

What is Perpetual Inventory System?

An inventory tracking method where stock levels are updated continuously in real-time with every purchase, sale, and adjustment.

How It Works

A Perpetual Inventory System maintains a running record of inventory quantities and values at all times — every inward (purchase, return) and outward (sale, issue, wastage) movement is recorded immediately. This contrasts with the Periodic System where stock is counted only at period-end. Modern ERP and POS systems use perpetual inventory with barcode/QR scanning. Benefits: real-time stock visibility, automatic reorder alerts, immediate COGS calculation, reduced stockouts, and better theft detection. Physical counts (cycle counting) are still done periodically to verify system accuracy.

Formula

Inventory Balance (at any point) = Previous Balance + Purchases – Sales – Adjustments (wastage, theft, damage)

Real-World Example

Product XYZ in ERP system: Opening (April 1): 500 units @ ₹100 = ₹50,000. April 3: Purchase +200 units @ ₹105. New balance: 700 units, value ₹71,000. April 5: Sale -50 units. Balance: 650 units. April 8: Wastage -5 units. Balance: 645 units. April 15: Cycle count finds 640 units (5 short — investigation needed). System shows real-time balance every moment.

Why It Matters

1

Ensures accurate financial reporting and record-keeping

2

Helps maintain regulatory and tax compliance

3

Enables better-informed business decisions

4

Improves operational efficiency and cash flow management

Frequently Asked Questions

What is the difference between Perpetual and Periodic inventory systems?

Perpetual: Updates stock with EVERY transaction (real-time balance). Uses technology (ERP/POS). COGS calculated per transaction. Periodic: Updates stock only at PERIOD END (monthly/annually) via physical count. Simpler but no real-time visibility. COGS = Opening + Purchases – Closing (calculated backward). Most modern businesses use Perpetual; very small retailers may still use Periodic.

Do you still need physical stock counts with a perpetual system?

Yes! Perpetual systems can have discrepancies from: theft/pilferage, data entry errors, damage not recorded, measurement errors, and system glitches. Cycle counting (counting a portion of items daily/weekly on rotation) is the best practice — you verify the entire inventory over a period (monthly/quarterly) without shutting down operations for a full count.

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