The EPC, or Electronic Product Code, is the primary identifier on a passive UHF RFID tag. When a reader inventories tags, the EPC is what comes back by default, so it is the value your software uses to decide which asset it has just seen. The EPC concept and its encoding schemes are defined by GS1, the standards body behind retail barcodes, and the air interface that carries it is the EPC Gen2 standard (ISO/IEC 18000-63).
Where the EPC lives on a tag
A Gen2 tag's memory is divided into four banks:
| Bank | Name | What it holds | Writable? |
|---|---|---|---|
| 00 | Reserved | Kill and access passwords | Yes, can be locked |
| 01 | EPC | The EPC, plus protocol-control bits and a CRC | Yes, can be locked |
| 10 | TID | Chip manufacturer, model and (on most modern chips) a unique serial | No — factory-set |
| 11 | User | Optional extra memory, if the chip has it | Yes, can be locked |
The EPC is commonly 96 bits long (24 hexadecimal characters), though many chips support longer EPCs. That is plenty to hold a unique identifier; it is not meant to hold a description of the asset.
EPC vs TID
The distinction matters for security and for reusing tags:
- The EPC is written by you (or your tag supplier) and can be rewritten, so a tag can be re-commissioned to a new asset when the old one is retired.
- The TID is burned in by the chip manufacturer and cannot be changed. On most modern chips it includes a unique serial number, so it identifies the physical chip itself.
Because the EPC is writable, someone could copy one asset's EPC onto another tag. Checking the TID alongside the EPC exposes that: the EPC matches, but the TID does not.
Encoding schemes: SGTIN, GIAI and others
GS1 defines structured EPC formats for different purposes. SGTIN (Serialized Global Trade Item Number) identifies an individual product instance and is widely used in retail. GIAI (Global Individual Asset Identifier) is designed specifically for identifying individual assets. GRAI covers returnable assets such as crates and kegs. Organizations that do not exchange tagged items with trading partners often use a simpler private numbering scheme — what matters is that each EPC is unique within your system.
Common mistakes
- Duplicate EPCs — pre-encoded tags from different batches can collide if you do not control the numbering. Check for duplicates when commissioning.
- Storing data in the EPC — encoding department or location into the EPC means it is wrong the moment the asset moves. Keep the EPC as a pure identifier.
- Ignoring the TID — without it, a cloned tag is indistinguishable from the original.
How Asetavo uses the EPC
Asetavo commissions each UHF tag by linking its EPC (and TID) to one asset in the register. Reader events carry the EPC, which Asetavo resolves to the asset to record audit counts, last-seen zone and movement. Tags can be decommissioned and reassigned, and clone detection flags an expected EPC that appears with an unexpected TID. UHF RFID is available on the Business plan.
