Ship classification guides

Guides to ship classification, IACS class status and how to check it, for chartering, vetting, insurance and compliance teams.

• Why does marine insurance depend on a ship keeping its class?

  How class status ties into hull and machinery and P&I cover, what suspension or withdrawal can mean for a policy, and how to monitor a book of vessels.

  19 October 2026
• What is the difference between class suspended and class withdrawn?

  Suspended class is temporary and can be reinstated. Withdrawn means the society no longer classes the ship. Causes, consequences and the numbers.

  19 October 2026
• How to check a ship's class status by IMO number

  Find the IMO number, look it up in the IACS Vessels in Class data, and read status, survey dates and reason fields correctly.

  19 October 2026
• What does it mean if a ship is classed by a non-IACS society?

  Ships classed outside IACS: why it raises due-diligence questions, how 431 ships moved to non-IACS class, and what the IACS data can and cannot show.

  19 October 2026
• What class red flags are associated with the shadow fleet?

  Class withdrawals, overdue surveys and moves to non-IACS societies: which class signals matter in shadow fleet screening, and what they cannot prove.

  19 October 2026
• How does the ship survey cycle work?

  Annual, intermediate and special surveys, bottom surveys in dry dock, and how to read survey dates and Survey overdue in IACS class data.

  19 October 2026
• What is a transfer of class and why do ships change classification society?

  Ships move between classification societies for ordinary commercial reasons, and sometimes to dodge scrutiny. How transfers work and what to check.

  19 October 2026
• What is a classification society?

  What ship classification societies do, how class differs from statutory certification, and why insurers, charterers, flags and lenders require it.

  19 October 2026
• What is an IMO number?

  The seven-digit IMO number identifies a ship for life. How the check digit works, who issues it, and why it beats name or MMSI for lookups.

  19 October 2026
• What is IACS?

  IACS explained: the 12 member class societies and their ship counts, Unified Requirements and CSR, and what the Vessels in Class dataset can tell you.

  19 October 2026
• IACS vessel classification data API: how to query class status by IMO number

  How to get class status, classification society and survey dates by IMO number from a REST API instead of the IACS ZIP/CSV download.

  25 March 2026