Inventory Management

How inventory management works

Inventory management follows a simple principle: starting from a verified opening stock, every goods movement is recorded as a posting. Receipts – for example from goods-in or production – increase the stock, while issues from sales, consumption or shrinkage reduce it. The uninterrupted sum of these movements yields the current book inventory at any point in time. What is tracked is not just a total value per item but usually the value per storage location, often additionally by batch, serial number or best-before date.

Modern systems distinguish several stock tiers: physical stock (what is actually on the shelf), available stock (physical stock minus reserved quantities) and expected stock from open orders. This differentiation is crucial so that an item is not sold twice while it is already reserved for another order. Stock is valued in parallel using commercial methods such as moving average, FIFO or the lower-of-cost-or-market principle under German commercial law.

Stock types and key metrics

Effective inventory management is not limited to plain counting; it steers stock through key metrics. It sets thresholds for each item at which actions are triggered automatically. This turns stock from a static number into an active planning instrument that triggers reorders before an item runs out and makes visible the excess stock that unnecessarily ties up capital.

Why inventory management matters

The benefit of precise inventory management is twofold: it secures availability while at the same time reducing tied-up capital. Anyone who does not know their stock either sells goods that are not there – with cancellations, back-orders and dissatisfied customers as a result – or holds excessive stock as a safety margin, which causes warehousing costs and ties up liquidity. Accurate, up-to-date inventory management resolves this conflict of goals by enabling a high service level with as little stock as possible.

Added to this is the legal dimension. The book inventory is the basis of stock valuation in the commercial and tax balance sheet. For the recorded figures to be recognised, stock movements must be logged in a traceable, complete and unalterable way – a requirement arising from the GoBD. Audit-proof inventory management is therefore not only sound from a business perspective but a prerequisite for proper bookkeeping. In multichannel sales, the aspect of stock availability across all sales channels is added: only centrally managed stock prevents overselling between shop, marketplace and brick-and-mortar sales.

Inventory management in the ERP system

In an ERP or merchandise management system, inventory management is a central module tightly interlinked with purchasing, sales, warehousing and accounting. Every document automatically triggers the matching stock movement: a goods-receipt posting increases the stock, a delivery to the customer decreases it, a return document books goods back in. Because all movements arise from the operational processes, no one has to maintain stock manually – currency results from day-to-day operations.

The prerequisite for this is clean master data: without unique item numbers, defined units and set-up storage locations, no system can post reliably. Advanced solutions manage stock multi-tier, across multiple entities and in real time, reserve goods on order entry and synchronise available quantities with connected online shops and marketplaces via interfaces. For complex warehouse processes with bin-location management and picking, inventory management interlocks with a warehouse management system (WMS) that steers the physical movement in the warehouse and reports back to the merchandise management system.

Distinction: inventory management, stocktaking and warehouse management

Inventory management, stocktaking and warehouse management are often conflated but mean different things. Inventory management is the ongoing accounting-based updating of quantities and values – it continuously supplies the target stock. Stocktaking is the periodic process in which the actual on-hand stock is counted and reconciled against the book inventory; it checks and corrects the result of inventory management. The more accurate the ongoing management, the smaller the stocktaking discrepancies.

Warehouse management, in turn, steers the physical side: where an item is located, how it is put away, picked and moved. It answers the question “where”, inventory management the question “how much and how much value”. In small operations, both coincide in a simple stock module; as warehouse complexity grows, a specialised WMS takes over bin-location control and reports stock changes to the merchandise management system. Perpetual inventory is only possible at all if inventory management is gap-free – here ongoing posting and sample-based counting merge into one continuous process.