FBA, FBM, WFS — and why your inventory tool needs to know the difference
Your fulfillment strategy directly affects how your inventory is tracked. Different fulfillment types mean different inventory deductions. Where an order ships from determines whether your warehouse inventory goes down. Get this wrong and your counts are fiction.
The rule is simple
If YOU shipped it → your warehouse inventory goes down.
If AMAZON or WALMART shipped it → your warehouse inventory stays the same.
Every inventory error in multi-channel selling comes from getting this wrong.
Amazon: Three fulfillment types, three different inventory effects
FBM — Fulfilled by Merchant
You store the product. You pick, pack, and ship it when an order comes in.
Inventory effect: FBM order → YOUR warehouse count goes DOWN.
This is straightforward. You had 50 units, you shipped one, now you have 49. Carpe Inventory IQ decrements your warehouse ledger.
FBA — Fulfilled by Amazon
You ship inventory to Amazon’s fulfillment centers in advance. When a customer orders, Amazon picks, packs, and ships.
Inventory effect: FBA order → Your warehouse count stays THE SAME. Amazon’s FBA count goes down.
This is where most inventory tools get confused. You didn’t ship anything — Amazon did, from stock you already sent them. Your warehouse still has whatever was already there. FBA inventory management requires tracking stock at Amazon's fulfillment centers separately from your own warehouse. Carpe Inventory IQ tracks FBA inventory separately via Amazon’s API and does not decrement your warehouse.
AWD — Amazon Warehousing & Distribution
Bulk storage that feeds FBA. You ship pallets to AWD warehouses. Amazon distributes units from AWD to FBA fulfillment centers over time as needed.
Inventory effect: AWD is a separate inventory pool. When Amazon moves units from AWD to FBA, your AWD count goes down and your FBA count goes up. Neither movement affects your warehouse.
Carpe Inventory IQ tracks AWD balances and AWD→FBA transfers so you see your complete Amazon supply chain: Warehouse → AWD → FBA → Customer.
The Amazon Inventory Flow
Your Warehouse
FBM Order
You ship
Customer
Warehouse −1
Ship to AWD
Warehouse ↓ AWD ↑
Amazon moves to FBA
AWD ↓ FBA ↑
FBA Order
Amazon ships
Customer
FBA −1, Warehouse unchanged
Your Warehouse
FBM Order → You ship → Customer
Warehouse −1
Ship to AWD
Warehouse ↓ AWD ↑
Amazon moves to FBA
AWD ↓ FBA ↑
FBA Order → Amazon ships → Customer
FBA −1, Warehouse unchanged
Your dashboard shows all three pools: Warehouse + AWD + FBA = Total Amazon inventory.
Walmart: Same concept, different names
Walmart FBM
Same as Amazon FBM. You store and ship the product.
Walmart FBM order → YOUR warehouse count goes DOWN.
WFS — Walmart Fulfillment Services
Walmart’s equivalent of FBA. You send inventory to Walmart’s fulfillment centers. They ship when customers order.
WFS order → Your warehouse count stays THE SAME. Walmart shipped from their stock.
Carpe Inventory IQ tracks WFS inventory separately, just like FBA.
Get it wrong and everything breaks
If your inventory tool decrements your warehouse when Amazon fills an FBA order, your warehouse count drops even though nothing left your warehouse. Within a week, your counts are wrong. Within a month, you’re overselling on some channels and sitting on phantom stockouts on others.
This is the most common inventory error in multi-channel selling, and it’s why most spreadsheet-based tracking breaks down when you add Amazon FBA.
Carpe Inventory IQ handles this automatically. You don’t configure it — the system knows which fulfillment type each order is and applies the correct logic.
Quick reference
| Fulfillment Type | Who Ships? | Your Warehouse | Tracked Where? |
|---|---|---|---|
| Shopify (you ship) | You | Goes down | Warehouse ledger |
| Amazon FBM | You | Goes down | Warehouse ledger |
| Amazon FBA | Amazon | No change | FBA inventory (API) |
| Amazon AWD | Storage | No change | AWD balance (API) |
| Walmart FBM | You | Goes down | Warehouse ledger |
| Walmart WFS | Walmart | No change | WFS inventory (API) |
Shopify (you ship)
Amazon FBM
Amazon FBA
Amazon AWD
Walmart FBM
Walmart WFS