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Cross-Channel Inventory Calculation

The Challenge

Anyone selling on multiple channels simultaneously faces a classic problem: Overselling. If the same stock is listed on Amazon, Otto, and Kaufland in parallel, it can happen that all three channels sell the same last item – and two buyers end up empty-handed.

At the same time, you want to display the available stock as high as possible to maximize sales opportunities.

The Solution: One Central Inventory Formula

The ALN MC Inventory Calc (CU 70024) calculates the optimal available quantity for each item and each channel – in a 10-step process:

Inventory Calculation: 10-Step Process

The 10 Steps in Detail

Step 1: Event Override

A connector can override the entire calculation via the event OnCalculateAvailableInventory. This is necessary e.g. for Amazon FBA, where Amazon manages the stock itself.

If overridden: Steps 2–9 are skipped.

Step 2: Fixed Quantity

If the Quantity Fixed flag is set in the Marketplace Item Card, the value entered there is used directly. No automatic calculation.

Use case: Promotional items with deliberately limited quantity or items that should not be automatically stock-managed.

Step 3: Calculate Base Stock

The BC standard calculation determines the available stock at the configured location:

Calculation Method Formula
Standard Stock on hand – pending outbound shipments
Reserved Stock on hand – reservations – pending outbound shipments
Full Complete BC availability calculation including incoming receipts

The method is configured globally in the merchantCENTRAL Setup.

Step 4: Add Supplier Stock

If the Include Supplier Stock option is enabled for the marketplace item, the stock of all suppliers from the Supplier Data Pool is added:

Own Stock:              50 units
+ Supplier Jarltech:    120 units
+ Supplier BlueStar:    30 units
─────────────────────────
Subtotal:               200 units

Important: Only suppliers with status "Active" and quantity > 0 are considered.

Step 5: Cross-Channel Deduction

To avoid overselling, the hub can deduct quantities reserved for other channels. The event OnGetChannelAllocatedQty queries all other marketplace connectors for how much stock they currently consider as "allocated".

Subtotal:               200 units
- Amazon Reservation:   20 units
- Otto Reservation:     10 units
─────────────────────────
After Cross-Channel:    170 units

Step 6: Deduct Safety Stock

The Safety Stock (per marketplace item or globally in the setup) is deducted from the quantity. This ensures you always keep a reserve in the warehouse.

After Cross-Channel:    170 units
- Safety Stock:         5 units
─────────────────────────
After Safety:           165 units

Step 7: Bundle Division

If a marketplace item is a bundle (e.g., 10-pack), the quantity is divided by the Bundle Content:

Individual Item Stock:  165 units
Γ· Bundle Content:       10
─────────────────────────
Available Bundles:      16 units

Step 8: Percentage Cap

Via the Quantity Percentage, you can specify that only a portion of the stock is displayed:

After Bundle:           16 units
Γ— Percentage:           80%
─────────────────────────
After Percentage:       12 units (rounded down)

Step 9: Maximum Cap

The Maximum Quantity limits the displayed quantity:

After Percentage:       12 units
Maximum Quantity:       10 units
─────────────────────────
Result:                 10 units (capped)

Use case: You don't want to show that you have 500 units in stock – that could give the impression the item is hard to sell.

Step 10: Channel Post-Processing

Via the event OnAfterCalculateAvailableInventory, each connector can adjust the final quantity – e.g., for FBA stock levels at Amazon or marketplace-specific special rules.

Configuration

Global Settings (merchantCENTRAL Setup)

Field Description
Inventory Method Standard / Reserved / Full
Include Supplier Stock Global default for new items
Global Safety Stock Default safety stock for new items
Cross-Channel Deduction Whether other channels are considered

Per Marketplace Item

Field Overrides
Quantity Fixed Entire calculation
Safety Stock Global default value
Maximum Quantity –
Quantity Percentage –
Include Supplier Stock Global default
Bundle Content –
Location Default location

Complete Example

Step Description Calculation Result
Base Stock at location WAREHOUSE 50 available 50
+ Supplier Jarltech + BlueStar 50 + 120 + 30 200
- Cross-Channel Amazon and Otto 200 - 20 - 10 170
- Safety 5 units minimum stock 170 - 5 165
Γ· Bundle Individual item (no bundle) 165 Γ· 1 165
Γ— Percentage 80% of stock 165 Γ— 0.80 132
Max Cap Maximum = 100 min(132, 100) 100

Result: Although 200 units are actually available, 100 units are reported as available on this channel.

Why This Matters

Avoid Overselling

Through cross-channel deduction and safety stock, the risk of selling an item that is no longer available is minimized.

Maximize Revenue

By including supplier stock, you can list items that you don't currently have in your own warehouse – and reorder at short notice if needed.

Flexible Per Channel

Each channel can have different inventory parameters – e.g., conservative on Amazon (high safety stock) and more aggressive in your own shop.

Fully Automatic

Inventory calculation runs automatically in the background. When your own stock or supplier stock changes, the marketplace quantity is automatically updated.