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 prevents duplicate-SKU errors and missing-item searches later.
The four identifiers at a glance
| Identifier | Created by | Example | Primary job |
|---|---|---|---|
| Custom label | Seller | A12-0047 |
Show a recognizable inventory reference |
| SKU | Seller or listing software | A12-0047 |
Identify the inventory record |
| 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 different. eBay does not know that A12 means the third tote on your west wall unless you choose to put A12 into the custom-label value.
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 through the Inventory API. That means the underlying eBay SKU must be unique even when a reseller wants several items to share a familiar bin label.
Can the custom label simply be the bin number?
Yes, if your workflow or listing software handles item uniqueness elsewhere.
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 ways to do that:
- Enter unique labels yourself:
A12-001,A12-002, and so on. - Keep
A12as the seller-facing label and let software create a unique technical key.
PileZero uses the second approach when labels repeat. It keeps the Custom label you entered and adds a stable suffix to the eBay SKU only where the Inventory API requires it.
What does PileZero show after listing?
Before publishing, PileZero shows the Custom label you chose or the label it generated. If that value can be used directly as the eBay inventory key, the two remain identical.
If the custom label is already in use, PileZero creates a unique eBay SKU by appending a short PileZero suffix. After publishing, the item shows both values when they differ:
| Field | Example |
|---|---|
| Custom label | A12 |
| eBay SKU | A12-PZ-7F7A9FE6 |
The first value is for the human workflow. The second is the durable remote identifier used for publishing, revisions, retries, and matching eBay activity back to the right PileZero item.
Where should each value appear?
Use the custom label or 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 or SKU. When investigating a listing-specific problem on eBay, use the eBay item number. When walking through the storage room, follow the bin location.
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 three layers:
- The bin tells you where to go.
- The custom label tells you what your system calls the item.
- The eBay SKU gives the marketplace a unique inventory key.
When all three layers agree, a sold item can move from order notification to shipping table without a search through the death pile.