🧭 Overview
When selling on Amazon, you’ll encounter two important identifiers:
SKU (MSKU) → Created by you for internal tracking
FNSKU → Created by Amazon for fulfillment tracking
Both are important, but they serve very different purposes.
🏷️ What is a SKU (MSKU)?
A SKU (Stock Keeping Unit) or MSKU (Merchant SKU) is a custom code created by the seller.
Purpose:
Track and organize your inventory
Identify products in your system
Manage listings across batches
Example:
BOOK-001SUPPLIER1-APR-123
👉 You control how SKUs are created
📦 What is an FNSKU?
An FNSKU (Fulfillment Network SKU) is a unique barcode assigned by Amazon for FBA items.
Purpose:
Tracks inventory inside Amazon warehouses
Links the item to your seller account specifically
Ensures the correct seller gets credited when an item sells
Example:
X001ABC123
👉 Generated automatically by Amazon for FBA listings
🔍 Key Differences
Feature | SKU (MSKU) | FNSKU |
Created by | Seller | Amazon |
Purpose | Internal tracking | Amazon fulfillment tracking |
Used for | Listing & inventory management | FBA warehouse identification |
Required label | No | Yes (for FBA items) |
Unique to seller | Yes | Yes |
⚙️ When Each is Used
SKU (MSKU)
Used in:
Listing items
Inventory management
Tracking batches
FNSKU
Used in:
FBA shipments
Labeling products before sending to Amazon
Warehouse scanning and fulfillment
⚠️ Important Notes
Every FBA item must have an FNSKU label
SKUs should be unique and consistent
FNSKU ensures your inventory is not mixed with other sellers
✅ Quick Summary
SKU (MSKU) = Your internal product code
FNSKU = Amazon’s barcode for FBA tracking
Both work together to manage and fulfill your inventory correctly