What is a transfer of class and why do ships change classification society?

What a transfer of class is

Every classed ship has one classification society that surveys it against its rules. A transfer of class moves that relationship from the losing society to the gaining society. The IMO number stays the same; the society, class notation and survey records change hands.

In the IACS Vessels in Class dataset, the losing society typically records the ship as Withdrawn with a reason such as Transfer of class to another IACS member or Transfer of class to a non-IACS society. If the gaining society is an IACS member, the ship should then appear in its records as in class, usually with the status Delivered. The status codes guide explains each status.

Transfers are common and mostly unremarkable. What matters is where the ship went, what state it was in when it left, and how often it has moved.

Why owners change classification society

Most transfers have ordinary commercial explanations:

• Change of owner or manager. A buyer often moves newly acquired ships to the society that already classes the rest of its fleet, so one team handles surveys and plan approval.
• Cost and service. Survey fees, surveyor availability in the ports the ship trades to, and response times all differ between societies.
• Financing or charter requirements. A lender or charterer may prefer, or require, particular societies.
• Flag change. Not every society is authorised by every flag state to act on its behalf, so re-flagging can force a change of class.
• Technical fit. Some societies have more experience with particular ship types or notations.

Some transfers are less benign. An owner facing an expensive survey, a difficult condition of class, or a society that is likely to withdraw class may look for a society that will take the ship with fewer questions. That is the pattern the IACS transfer procedures, and many due diligence checks, are designed to catch.

The IACS Transfer of Class Agreement (TOCA)

IACS members apply a common procedure when a ship moves from one member to another, widely known as the Transfer of Class Agreement, or TOCA. The detail sits in IACS procedural requirements and changes over time, so check the current text on the IACS website before relying on specifics. In general terms, the arrangement is designed so that:

• The losing society shares the ship's survey status and history with the gaining society, including outstanding conditions of class and recommendations.
• Overdue surveys and overdue conditions of class are typically dealt with before, or as part of, the transfer, rather than disappearing with the change of society.
• The gaining society carries out its own survey of the ship as part of accepting it into class, with the scope usually depending on the ship's age and survey position.
• Outstanding items are carried over, so the ship does not start with a clean sheet it has not earned.

The intent is simple: changing society should not be a way to avoid a survey or a finding. TOCA applies between IACS members. A move to a society outside IACS is not covered by the same shared procedure, which is one reason it gets more attention. See what is IACS and non-IACS classification societies.

Class hopping as a risk pattern

Class hopping is the informal name for moving a ship between societies to avoid the consequences of its condition: an overdue survey, a costly repair, or a looming suspension or withdrawal. It is a pattern, not a recorded status. You infer it from the history.

Signals that commonly prompt a closer look:

• A transfer to a non-IACS society, especially on an older ship.
• A transfer that follows closely after a suspension, an overdue survey or a non-compliance finding.
• More than one change of society in a short period.
• A transfer at around the same time as a change of name, flag, owner or manager.
• A ship that leaves IACS class and then disappears from the IACS data altogether.

None of these proves wrongdoing. Plenty of older ships move to smaller societies for cost reasons near the end of their trading life. But in sanctions, KYC and vetting work, these are the patterns most often associated with ships that are harder to inspect, insure or trace. See class checks for sanctions and KYC screening and shadow fleet class red flags.

What the data shows

In the IACS snapshot of 30 September 2026 (60,223 ships across the 12 members), the latest recorded status change for 1,747 ships was a transfer of class:

• 1,316 with the reason Transfer of class to another IACS member.
• 431 with the reason Transfer of class to a non-IACS society, roughly a quarter of all recorded transfers.

The split varies a lot by losing society:

Two cautions. First, these counts only reflect the reason on each record's latest status change; many older transfers will have been overwritten by later events, and a society that records most withdrawals as by society for other reasons will show fewer transfers here. Second, the counts describe the losing society's records and say nothing about the gaining society's standards. Treat the table as a description of the dataset, not a ranking of societies.

What to check when a ship has changed class

1. Current status. Look the IMO up and confirm the ship is in class now, with which society. The free lookup on Vessel Class Finder shows one ship at a time, for example IMO 9811000; the API checks up to 100 IMOs per request.
2. The reason and the date. Read reason_for_status with date_of_latest_status. A recent transfer deserves more attention than one ten years ago.
3. Where it went. If the reason says non-IACS, the ship will not appear in IACS data afterwards. Ask the owner which society classes it now and request the class certificate.
4. What came before. Ask whether the ship was suspended, had a survey overdue or had open conditions of class at the time of transfer.
5. Surrounding changes. Compare the transfer date with any change of name, flag, owner or manager from your other sources.
6. Contract terms. Check whether the new society meets your charter party, policy or loan requirements, which often specify an IACS member.

Class data covers only ships classed by the 12 IACS members and is refreshed weekly. It is one input alongside sanctions screening, ownership research and inspection history, not a replacement for them.

Frequently asked questions

Related

• What is the difference between class suspended and class withdrawn?
• What does it mean if a ship is classed by a non-IACS society?
• What class red flags are associated with the shadow fleet?
• Vessel class checks for sanctions and KYC screening
• All articles