How FBA inventory is tracked
Amazon, not you, moves the stock in its fulfillment centers. It receives your shipments, ships orders, takes returns back, moves units between buildings, and records units it loses, finds, damages or disposes of. Every one of those events lands in Amazon's inventory ledger. SKU.io reads that ledger and treats it as the record of what happened to your FBA stock, so you never key in an FBA adjustment yourself.
Where the numbers come from
SKU.io pulls two Amazon reports for each connection, from your tracking start date on:
| Report | What it holds | Where you see it |
|---|---|---|
| Inventory ledger (detail) | One row per event: a receipt, a shipment, a customer return, a removal, a transfer between fulfillment centers, or an adjustment. Refreshed every hour. | Inventory & Valuation → Ledgers |
| Ledger summary | Each product's opening balance, movements by type, and closing balance, per day and per condition (sellable or unsellable). Amazon treats it as the count of what you hold. Refreshed every night. | Inventory & Valuation → Ledger Summaries |
Amazon's FBA inventory report, shown on the Inventory tab, is a third view. It's a snapshot of where units sit right now (fulfillable, reserved, inbound and so on), and it doesn't move your stock. See Read FBA stock by state.
How each event is classified
Every ledger row has an Event Type: Receipts, Shipments, Customer Returns, Vendor Returns (removals), Warehouse Transfers or Adjustments. Adjustments carry Amazon's Reason code, which says what kind of adjustment it was. The main groups are:
- Lost: for example, misplaced in the fulfillment center.
- Found: units Amazon located again.
- Damaged: by Amazon, a carrier, a customer or the distributor.
- Disposed: destroyed or disposed of by Amazon.
- Corrections and condition changes: units moving between sellable and unsellable.
How each event is valued
SKU.io values FBA stock with FIFO cost layers:
- A unit arriving (a receipt, a return, a found unit) opens a cost layer. The cost comes from the purchase order or transfer that sent it, or from the opening cost you entered under FNSKU Products (Initial Costs).
- A unit leaving (a shipment, a removal, a loss) uses up the oldest layers first. Each use is listed under Inventory & Valuation → Consumptions.
Each ledger row also posts to your books. Units Amazon ships or removes move their cost out of FBA inventory into cost of goods sold. Losses, finds, damage and disposals go to your receiving discrepancies account, which is where FBA reimbursements then offset them.
Keeping detail and summary in step
Sometimes Amazon's detail rows don't add up to its own summary, because a row is missing or an event is one SKU.io doesn't recognize. Each night SKU.io compares the two for every product, and adds a corrective discrepancy ledger entry for the difference, so your stock always ends at Amazon's summary figure. You don't have to act on these for your counts to be right, but you can look into them. See Investigate FBA ledger discrepancies and cost exceptions.