Overview

On March 15 2024 Amazon announced that the Quantity field in the POST_INVENTORY_AVAILABILITY_DATA feed applies solely to inventory that the seller ships directly, such as Seller‑Fulfilled Prime or Merchant‑Fulfilled (MFN) listings. Amazon‑fulfilled (FBA) SKUs ignore any manual quantity values because the fulfillment centers automatically adjust stock levels. Sellers must recognize this separation to prevent feed rejections, inventory discrepancies, and possible listing suspensions.

Key Points

• Applicable SKUs — The Quantity attribute updates only merchant‑shipped items; any SKU marked as FBA will not accept the value.
• Automatic FBA sync — Amazon continuously reconciles FBA inventory, so manual submissions for those SKUs are discarded without error.
• Error code — When a seller includes Quantity for an FBA‑eligible ASIN, the feed response returns an InvalidQuantityForFBA error.
• Split fulfillment — Products that are stocked partly in Amazon’s warehouses and partly in the seller’s own location require separate feed entries for each fulfillment node.
• Processing speed — Updates to merchant‑fulfilled stock become visible within roughly 15 minutes, while FBA inventory changes propagate automatically in the same timeframe without a feed.

How the Quantity Attribute Works

1. Determine fulfillment type — Check the fulfillment channel for each SKU in the Manage Inventory page.

   • Example: SKU XZY987 shows “Fulfilled by: Merchant,” indicating it can be updated with the Quantity field.

2. Assemble the inventory file — Create a tab‑delimited or XML document that contains at least sku, quantity, and fulfillment_latency. The quantity value must match the exact units physically available at the seller’s warehouse.