IMO number
The seven-digit unique + permanent identifier assigned to a ship by the IMO — remains with the hull for its entire life regardless of flag + name changes.
Regulatory detail & full definition
IMO number is the seven-digit unique + permanent identifier assigned by the IMO to every ship of 100 GT + above. Remains with the hull for its entire life — flag changes, name changes, ownership changes do not change the IMO number. Displayed permanently on the hull + within the accommodation space per SOLAS XI-1/3. Powers cross-reference across every maritime database (Equasis, Class registers, PSC databases, sanctions lists). See /ships/[imo] for individual ship pages.
Authoritative source: IMO — Numbering Scheme ↗
Related
Source: SOLAS XI-1/3 + IMO Res. A.600(15)
High confidence
Editorial confidence: how we grade.