# Identifier Collision Identifier collision occurs when the same number, token, acronym, or name appears in different systems without establishing a causal or technical relationship. ## Source example [[Scanned_20260730-1235|Scanned_20260730-1235]] compares the Federal Register citation `66 FR 49829` with EMV tag `66`. Both are meaningful identifiers, but their shared number is not evidence that the systems are connected. ## Archival rule Record the collision as a research lead while distinguishing coincidence, shared standard lineage, copied implementation, direct interoperability, and causal integration.