SKU

 An SKU is a foundational inventory management identifier across Amazon’s retail, FBA, and vendor ecosystems.
It allows Amazon and sellers to track stock levels, shipments, sales performance, and replenishment needs accurately for each unique product variation.

SKUs are internal identifiers - created and managed by the seller or vendor - and differ from Amazon’s global product identifiers such as ASIN (Amazon Standard Identification Number) or UPC (Universal Product Code).

Key Characteristics of SKUs:

• Unique per product: Every variation (e.g., “red T-shirt, size M”) has its own SKU.
• Customisable: Vendors and sellers define their own SKU structure.
• Non-global: An SKU is internal to a specific account or system, not universal like an ASIN.

Example SKU Structure:
A seller can define SKUs using any logic, for example:
BLD-TSHRT-RED-M
where

• BLD = brand code (BoldLine),
• TSHRT = product type (T-shirt),
• RED = colour,
• M = size.

SKU vs ASIN vs FNSKU:

IdentifierPurposeAssigned ByScopeSKU | Seller/vendor’s internal product code | Seller or vendor | Account-specific
ASIN | Amazon’s unique product ID | Amazon | Marketplace-wide
FNSKU | Fulfilment identifier for FBA inventory | Amazon | FBA system

Uses of SKUs on Amazon:

1. Inventory Management:
   • Track available stock across FCs, warehouses, and inbound shipments.
2. Sales Tracking:
   • Monitor performance metrics (e.g., revenue, units sold, return rate).
3. Replenishment Planning:
   • Link SKUs to lead times (VLT/PLT) and automate purchase orders.
4. Reporting and Analytics:
   • SKUs appear in Amazon Retail Analytics (ARA), Vendor Central, and Seller Central reports.

Benefits for Amazon:

• Enables precise fulfilment and shipment tracking.
• Supports accurate product mapping to ASINs and listing data.
• Enhances inventory accuracy and forecasting.

Benefits for Vendors and Sellers:

• Provides control and flexibility in inventory management.
• Allows for custom grouping by brand, category, or variation.
• Facilitates data reconciliation across multiple sales channels.

Challenges:

• Inconsistent naming: Poor SKU structure can cause reporting confusion.
• Duplication risk: Different SKUs for the same ASIN can create data discrepancies.
• Scaling issues: Complex SKU hierarchies can become hard to maintain as catalogues grow.

Best Practices:

• Use a logical, standardised naming convention.
• Keep SKUs short (10–20 characters) but descriptive.
• Avoid special symbols or spaces.
• Align SKU structure across all internal systems (ERP, Vendor Central, FBA, etc.).

Example:
A vendor selling a stainless-steel blender assigns SKU BLD-BLEND500-SIL for the silver model.
When Amazon ships 500 units under this SKU, all sales, replenishment, and reporting data tie back to it in Vendor Central and ARA dashboards.

In short:
SKU (Stock Keeping Unit) is a seller- or vendor-defined unique identifier for each product variation, used to manage inventory, sales, and fulfilment data across Amazon’s systems.