Resellers often use SKU, custom label, and bin number as if they mean the same thing. They can contain the same text, but they describe different parts of the inventory system.
The shortest explanation is:
- Custom label: the seller-facing field where you enter your inventory code.
- SKU: the inventory identifier represented by that field and used by eBay’s APIs.
- Bin location: the physical place where the item is stored.
- eBay item number: the public listing identifier created by eBay.
Understanding the distinction helps you choose a label that matches the way you store and retrieve inventory.
The four identifiers at a glance
| Identifier | Created by | Example | Primary job |
|---|---|---|---|
| Custom label (SKU) | Seller or listing software | A12 or A12-0047 |
Track a location, item, or both |
| Bin location | Seller | A12 |
Identify physical storage |
| eBay item number | eBay | 123456789012 |
Identify the published listing |
In many eBay screens, Custom label (SKU) is one combined field. eBay’s developer documentation also describes inventory reference IDs as “SKU” or “custom label.” That is why the terms are commonly interchangeable in conversation. See the eBay inventory reference definition.
The physical bin is still a real-world location, but many sellers put that location directly in Custom label (SKU). Others use a unique item code and track the bin elsewhere. eBay stores the text; your workflow gives it meaning.
What is a custom label on eBay?
The custom label is a seller-controlled field used to track inventory. It is not the listing title and is not meant to persuade a buyer. Sellers use it for warehouse locations, internal catalog numbers, supplier codes, or a combination of those values.
In Seller Hub and reports, a useful custom label can make an order immediately actionable. Instead of recognizing the product and remembering its location, the seller reads A12-0047 and goes directly to bin A12.
The field can be up to 50 characters according to eBay’s SKU documentation, but an operational label should usually be much shorter.
Why does eBay sometimes require a unique SKU?
There are two eBay listing architectures behind advice you may find online.
The older Trading API can associate the same SKU with multiple items in some configurations. By contrast, eBay’s Inventory API defines every inventory item by a seller-created SKU that must be unique within that seller’s inventory. An inventory item must exist before an offer can be published. See eBay’s Inventory API overview.
PileZero publishes new listings through the Trading API and tracks them by eBay item ID. In that setup, the seller’s Custom label (SKU) does not need to be unique. PileZero therefore supports both repeated location labels and unique item labels.
Can the custom label simply be the bin number?
Yes. If your workflow treats the custom label as a pull location, several listings can use A12.
Suppose eight shirts are stored in bin A12. Using A12 as the recognizable label is convenient because the order tells you exactly where to start. But the inventory system still needs to distinguish one shirt from the other seven.
There are two straightforward ways to organize those shirts:
- Enter unique labels yourself:
A12-001,A12-002, and so on. - Use
A12on all eight listings and confirm the exact shirt from the title, photo, size, or another physical tag.
PileZero supports both approaches and sends the label exactly as entered.
How does PileZero store these values?
PileZero stores one Custom label (SKU) value, matching the field in eBay’s listing form. It does not create a separate Bin value or force a unique suffix.
The field is optional, may be reused across items, and remains editable after listing. A label photo can also supply the value during AI generation while staying out of the public photo set.
Where should each value appear?
Use the SKU in:
- Your PileZero item record
- eBay Seller Hub columns and reports
- Inventory spreadsheets or cross-listing records
- A printed or written item tag
Use the physical bin label on:
- Shelves, totes, racks, or drawers
- Item bags when the location is part of the SKU
- A storage map if the workspace has multiple zones
Use the eBay item number when:
- Communicating with eBay support
- Opening the exact public listing
- Reconciling an eBay-specific listing event
Do not substitute the eBay item number for your own inventory system. It does not exist until publishing and does not naturally tell you where the item is stored.
Which identifier should you search?
When looking for an item in your own inventory, search by Custom label (SKU). When investigating a listing-specific problem on eBay, use the eBay item number. When walking through the storage room, follow whatever physical location system your custom labels represent.
These identifiers should connect to one another, but they do not need to be identical. A strong inventory workflow preserves the value that is useful to the seller while satisfying the identifier rules of the marketplace.
The practical rule
Think of the system as two seller choices plus one eBay identifier:
- Your Custom label (SKU) follows the tracking method you choose.
- Your physical labels use the same meaning consistently.
- The eBay item number identifies the published listing.
When those values agree, a sold item can move from order notification to shipping table without a search through the death pile.