What class red flags are associated with the shadow fleet?
Class signals often associated with shadow or dark fleet risk are: class withdrawn or suspended, especially for an overdue survey; a transfer to a non-IACS society; no IACS class record for a ship trading internationally; and a recent status change on older tonnage. Each one is an indicator, not proof. Combine it with sanctions screening, AIS history, ownership research and P&I checks before drawing conclusions.
Why class comes up in shadow fleet screening
'Shadow fleet' and 'dark fleet' are informal labels. They usually describe ships, often older tankers, that trade outside the mainstream system of Western-linked insurance, finance and services, sometimes to move sanctioned cargo. There is no official list and no single definition. In December 2023 the IMO Assembly adopted a resolution urging states and the industry to act against illegal operations by the 'dark fleet', which shows the issue is taken seriously, but it did not create a register of ships.
Classification matters because mainstream insurers, banks, charterers and port authorities typically expect a ship to hold class with a recognised society, usually one of the 12 members of IACS. A ship that leaves that system loses one of the routine, independent checks on its condition. That makes class status one of the few public, structured data points a compliance team can check by IMO number in seconds.
The class signals worth a closer look
The IACS Vessels in Class dataset records a status and, for many ships, a reason for the latest status change. In the snapshot of 30 September 2026, covering 60,223 ships, these are the patterns most relevant to screening:
- Withdrawn for 'Survey overdue': 1,589 ships carry this reason. The owner did not complete a required survey on time and the society ended class.
- 'Transfer of class to a non-IACS society': 431 ships. The ship moved out of IACS class. See non-IACS classification societies for why that matters.
- Withdrawn 'by society for other reasons': 3,645 ships. This is a broad category with many routine causes, so it needs reading in context.
- 'Non-compliance with conditions of class / recommendations': 178 ships. The society required repairs or actions that were not carried out.
- Suspended: 575 ships currently suspended. Class is not in force until the issue is resolved.
- No IACS record at all for an ocean-going ship. It may be classed by a non-IACS society, or have no class.
- A next survey date in the past on a ship that is still trading.
- A recent status change on an older ship, particularly a tanker. Shadow fleet reporting commonly describes ships of 15 to 20 years or more.
A single signal is a reason to ask questions. Two or three together, on the same ship, deserve enhanced due diligence. The IACS class status codes page explains each status in detail.
Every signal has ordinary explanations
Most ships with these flags are not part of any shadow fleet. Treat class data as a filter that tells you where to look, never as a finding.
| Signal | Common innocent explanation | What to ask |
|---|---|---|
| Withdrawn, survey overdue | Ship laid up, sold for demolition, or owner in financial difficulty | Is the ship trading? Has it been reclassed elsewhere? |
| Transfer to non-IACS society | Domestic or regional trade where a national or smaller society is normal and accepted | Which society now? Is it recognised by the flag state? Where does the ship trade? |
| Suspended | A survey window missed by days, often fixed quickly | When was it suspended, and has it been reinstated since? |
| No IACS record | Small, domestic or newly delivered ship, or a typing error in the IMO number | Check the IMO number, then ask for the class certificate |
| Withdrawn, other reasons | Sale, scrapping, change of manager or flag paperwork | What happened next? Any new class? |
The data itself shows how common routine causes are: 1,316 ships carry 'Transfer of class to another IACS member' and 266 'Sold for recycling (scrap)'. Moving between IACS societies is normal commercial behaviour. Our guide to transfer of class covers how those moves usually work.
What class data can and cannot tell you
It can tell you:
- Which IACS society holds the record, and the current status.
- The reason recorded for the latest status change.
- The date of the last survey, the next survey due and when the current status took effect.
- Whether the IMO number appears in the IACS dataset at all.
It cannot tell you:
- Who owns, manages or controls the ship. Class data has no ownership fields.
- Whether the ship, owner or cargo is sanctioned.
- Where the ship has been, or whether its AIS transponder went dark.
- Who insures it, or whether that insurance is genuine.
- The ship's age, flag or type. Those come from registry data.
- Anything about ships classed only by non-IACS societies. They are simply absent.
It is also a snapshot. The public IACS dataset is published as a periodic download, and Vessel Class Finder refreshes it weekly, every Sunday. A change made by a society yesterday may not show yet. For a decision, the society's own records and the class certificate remain the authority.
How to combine class with other checks
Class is one independent layer. A reasonable screening file on a ship typically brings together five:
- Sanctions screening. Match the IMO number, ship name, registered owner, manager and related companies against the sanctions lists that apply to you. Class data does none of this.
- Class status. Check status, reason and survey dates by IMO. Note anything from the list above.
- AIS and voyage history. Look for transponder gaps, unexplained loitering, ship-to-ship transfers in open water, and port calls that do not match the stated trade.
- Ownership and management. Look for recent changes of owner, single-ship companies, frequent changes of name or flag, and registered addresses that reveal little.
- P&I and hull insurance. Ask who provides P&I cover. Cover from a member of the International Group of P&I Clubs is easy to verify. Cover from an unfamiliar provider needs more work.
The value is in the overlaps. A ship that left IACS class, changed owner and flag in the same few months, and has gaps in its AIS track tells a different story from a ship with only one of those features. Our sanctions and KYC screening page sets out a step-by-step workflow for the class part.
Building class checks into a routine
One-off checks miss changes. Ships lose class between deals. A practical routine looks like this:
- Check at onboarding. Record the class society, status and date of latest status in the case file, with the date you checked.
- Re-check before each transaction such as a charter, cargo purchase, loan drawdown or port call.
- Monitor portfolios weekly. Compare this week's results with last week's and flag any change of status, any change of society, and any next survey date that has passed.
- Escalate by combination, not by single flag. Send ships with two or more signals to enhanced due diligence.
- Ask for documents. When a flag appears, ask the owner or manager for the current class certificate and survey status report from the society.
You can try one ship with the free lookup, for example EVER GIVEN (IMO 9811000), which shows ABS as society, status Delivered and a next survey due 24/09/2028. For lists of ships, the vessel classification API takes up to 100 IMO numbers per request.
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Get a free API keyFrequently asked questions
What is the shadow fleet in shipping?
It is an informal term for ships, often older tankers, that operate outside mainstream insurance, finance and classification, sometimes to carry sanctioned cargo. There is no official list or single definition.
Is losing class a sign that a ship is in the shadow fleet?
Not on its own. Class is lost for many routine reasons, such as lay-up, sale or scrapping. It is an indicator that justifies more checks, especially when combined with ownership changes, AIS gaps or unclear insurance.
Why does a transfer to a non-IACS society matter?
IACS members work to common technical requirements and procedures. A move outside IACS means mainstream insurers, charterers and banks may have less assurance about the ship's condition. Many such transfers are legitimate, for example for domestic trade.
Can class data show who owns a vessel or whether it is sanctioned?
No. The IACS dataset has no ownership or sanctions fields. Use a sanctions screening tool and ownership research alongside class data.
What does it mean if a ship is not in the IACS dataset?
It is not classed by one of the 12 IACS members. It may be classed by a non-IACS society, have no class, or the IMO number may be wrong. Check the number first, then ask for the class certificate.