Let us to distinguish between Amazon co-location and sub-location.

These combined warehouses mean that FBA products are collected together in the same Amazon warehouse. The split warehouse means that Amazon will divide the same batch of Cargo and products of the same SKU created by sellers into 1 to 3 FBA warehouses.

It creates FBA shipping orders in the background. There will be two choices in the inventory configuration option In inventory place option , it said the inventory placement services, distributed inventory place (sub-warehouse). The default setting is to split the warehouse.

1. Why Amazon default split warehouse ?

The reason why Amazon separates sellers' products into warehouses, it is to improve the reasonable utilization of the warehouse and prevent the warehouse from bursting or being vacant. Amazon combined with the seller's product type to do a comprehensive analysis according to the conditions of each FBA warehouse facilities, temperature, humidity and other factors, then each product will be assigned to the most appropriate FBA warehouse. 

2. It will save Amazon FBA delivery fee

Amazon distributed the seller's inventory to multiple Amazon operating centers in order to save itself money. Buyers are able to save on FBA delivery costs while purchased products had compared to the case where the inventory is far away.

3. To calculate fees for the co-location & sub-location

FBA fees is equal to Fulfillment Fees (implementation fees) + Monthly Storage Fees (monthly storage fees) + Inventory Placement Service (inbound inventory placement service fees).Fulfillment Fees is equal to Order Handling+Pick & Pack+Weight Handling.

Sellers from Amazon are charged a fee for proactive consolidation and splitting of warehouses. This fee is classified as Inventory Placement Service and inbound inventory placement service fee.