Vendor catalog: item identity, packaging hierarchy, and account context

• ASIN — Amazon's catalog identifier, shared with every seller and Amazon Retail; the same ASIN can be supplied by a vendor and sold by third parties at once.
• GTIN (Global Trade Item Number), at every packaging level — the GS1-issued barcode numbers. The consumer unit carries its UPC or EAN (12- and 13-digit GTINs); the case carries its own GTIN-14 (ITF-14 barcode). Never put a case code in the unit field.
• Vendor code — identifies your vendor account; one company can hold several (country, category, legal entity). Every item lives under one, and catalog views, reports and cases are scoped to it.
• Your own item number — the vendor SKU field (model number in some templates). Amazon stores it so reports and cases match back to your systems. Read the headers: in Vendor Central's templates external ID normally means the product's GTIN, with an external ID type beside it, not your number.

Keep all four in one row of your source of truth: a support case citing the ASIN but the wrong vendor code goes nowhere.

Vendor items are set up as a hierarchy, and the fields are not interchangeable:

• Each (consumer unit) — what the customer receives: its UPC/EAN, dimensions, weight and content describe one sellable unit.
• Inner pack — where the template offers it, a bundle of eaches inside the case, with its own quantity and sometimes its own GTIN.
• Case — how you ship to Amazon's fulfillment centers: case quantity (eaches per case), case GTIN-14, case dimensions and weight.
• Pallet — layer and tie-high configuration for large volumes.

A figure that is right for the unit is wrong for the case. Amazon uses case data to write purchase orders and route inbound freight, so a unit dimension in the case field, a case quantity of one for a case of twelve, or the unit UPC in the case GTIN field produces wrong purchase-order quantities, chargebacks and refused shipments — not a listing error. Nothing on the detail page warns you; enter every level from the approved packaging specification.

Before any workflow, confirm three things.

Which vendor code. The account switcher (in most accounts) sets the vendor code everything you do is filed under. Submitting a perfectly correct item under the wrong code is easy and silent: the item is approved, and colleagues under the right code never see it.

Which marketplace. amazon.com, amazon.co.uk, amazon.de and the rest each have their own catalog — usually under their own vendor code, and in many regions behind their own login. An ASIN set up in one does not exist in another until you set it up there, and content, images and families are per marketplace.

Whether the ASIN is already in that catalog. Items → Catalog (the label changes) lists every ASIN under the vendor code you are in, with its availability status; check it before you search Add Products.

A login that can view the catalog may not be able to submit items or open cases, so check permissions before you report a missing feature.

Open Items → Add Products and search by the consumer unit's GTIN first, then by ASIN if you were given one. Two outcomes:

Match. The ASIN exists — created by a seller, Amazon Retail, or another of your vendor codes. Add it to your catalog: that files the ASIN under your vendor code with your unit and case data, so Amazon Retail can source the product from you and your content attaches to the page. You create no listing and hold no offer. Correct its content afterwards (Content updates). Never create a second ASIN from the same GTIN: Amazon merges duplicates eventually, and the merge can take your content and your purchase-order history with it.

No match. New item setup, in Add Products or a setup spreadsheet:

1. Choose the product type.
2. Complete its required attributes.
3. Enter the unit and case data, each at its own level.
4. Submit, then read the submission status; a rejected row is fixed at its source (Unavailable pages).

In most accounts the Items menu holds the catalog work (labels change):

• Catalog — every ASIN under the vendor code, with status.
• Add Products — search, add existing ASINs, set up new items one at a time.
• Edit Products — change detail page content on ASINs already in your catalog.
• Bulk product submissions — the new item setup (NIS) spreadsheet and update spreadsheets; submission status sits here or under a separate product submissions entry.

Support → Contact Us (labelled Help in some accounts) and the Case Log handle whatever no submission can; Support → Resource Center holds Amazon's own vendor guides, behind login.

The track is one workflow:

1. Setup — this module; submission errors in Unavailable pages.
2. Content — Content updates for text, Media and A+ Content for images and modules, Variation families for parents and children.
3. Readiness — Retail readiness reviews the whole page and whose contribution displays.
4. Cases — Case management, when a submission cannot fix it.