The TID lives in its own memory bank on a UHF RFID chip. It is programmed by the chip manufacturer and locked, so it cannot be rewritten. It identifies the manufacturer and chip model and, on most modern chips, includes a unique serial number (sometimes called a serialized or extended TID) — making it an identity for the physical chip itself rather than the asset it is attached to.
TID vs EPC
The EPC is the identifier you write and can rewrite; the TID is fixed. Most systems use the EPC to identify the asset, and the TID as a check that the tag is the one originally commissioned.
Why it matters
Because EPCs are writable, a determined person could copy an asset's EPC onto a different tag. If you recorded the TID at commissioning, a read that shows the right EPC with the wrong TID is a red flag: the tag has been cloned or swapped.
In Asetavo
Asetavo can store the TID alongside the EPC at commissioning and uses it for clone detection when tags are read.
