Operational Guide · Registers & Logbooks

# Managing Surveys under Dual/Multiple Classification

When a ship is classed by two Societies (dual/double class), survey cycles do not simply add up: without a clear Bilateral Agreement between the Societies, the risk is needlessly duplicating surveys or, worse, leaving gaps in coverage.

dual class IACS classification survey transfer of class

## Operational Explanation

Some ships, for commercial reasons or to meet the requirements of specific markets/financiers, maintain simultaneous classification with two Classification Societies (dual class or double class). In these cases, coordination between the two Societies is governed by a Bilateral Agreement defining which Society is responsible for which surveys, how outcomes are shared, and what happens if one of the two classes is suspended or withdrawn.

The IACS procedural framework (Procedural Requirement PR-1, which governs Transfer of Class) also applies, with appropriate adaptations, to managing dual/multiple classification, including the concept of the "Remaining Society" — the Society that keeps the ship in class when the other suspends or withdraws its own classification.

## Regulatory Reference

IACS Procedural Requirement PR-1 (Transfer of Class) framework, extended to managing dual/double classification through a Bilateral Agreement between the Societies involved; each IACS Classification Society also maintains its own detailed technical publications on managing dual/double class (e.g. Publication 97/P of the Polish Register of Shipping, in force from 1 January 2026).

## Scope of Application

Ships simultaneously classed by two Classification Societies (dual/double class), with coordination responsibility shared between the Company and the two Societies involved.

## Procedure / How to Complete It

1. Verify the existence and contents of the Bilateral Agreement between the two Classification Societies involved before planning the survey cycle.
2. Clarify which Society is responsible for each survey (Annual, Intermediate, Renewal) under the agreement, avoiding both duplication and coverage gaps.
3. Ensure that the outcomes of every survey conducted by one Society are formally shared with the other, per the terms of the bilateral agreement.
4. In the event of suspension or withdrawal of class by one of the two Societies, immediately identify the 'Remaining Society' and the implications for the validity of the related statutory certificates.
5. Promptly coordinate with both Societies any Condition of Class or Recommendation issued by either, to avoid conflicting interpretations.

## Practical Example

Example: a ship in dual class between two IACS Societies has a Bilateral Agreement assigning the hull Renewal Survey to Society A and the machinery Renewal Survey to Society B; the outcomes of each survey are formally transmitted to the other Society within an agreed timeframe, keeping both classes aligned on the ship's actual condition.

## Real Cases

Managing dual class without a clearly applied bilateral agreement has historically generated cases of duplicated surveys (with additional cost and time for the owner) or, in worse scenarios, coverage gaps when both Societies assumed the other had already conducted a specific check: hence the ongoing update of the IACS PR-1 framework and individual Societies' publications to clarify responsibilities.

## Common Mistakes Mistake Library

Mistake | Consequence | How to avoid it
--- | --- | ---
Bilateral Agreement between the two Societies not verified or not up to date before planning the survey cycle | Duplicated surveys or coverage gaps between the two classes | Always verify the up-to-date contents of the Bilateral Agreement before every survey planning cycle
Outcomes of a survey conducted by one Society not formally shared with the other Society in dual class | The two classes remain misaligned on the ship's actual condition | Ensure formal, timely transmission of outcomes per the terms of the bilateral agreement
Suspension of class by one Society not immediately handled by identifying the Remaining Society | Uncertainty over the validity of the statutory certificates tied to the suspended class | Immediately identify the Remaining Society and the implications for certificates in the event of suspension/withdrawal of one of the two classes

## PSC Observations

PSCOs check consistency between the class certificates presented and the ship's actual condition; in the case of dual class, discrepancies between the outcomes reported by the two Societies can generate additional requests for clarification during inspection.

## Operational Tips

- Always request an up-to-date copy of the Bilateral Agreement from the two Societies involved; do not rely on outdated versions or informal understanding.
- Maintain clear traceability of which Society conducted which survey and when outcomes were shared with the other.
- In case of doubt over the division of responsibilities between the two Societies, clarify in writing before the survey, not after.

## Checklist

- Bilateral Agreement between the two Societies verified and up to date
- Responsibility for each survey clearly assigned per the agreement
- Outcomes of every survey formally shared between the two Societies
- Remaining Society procedure known in the event of suspension/withdrawal of a class
- Condition of Class/Recommendations coordinated between both Societies

## FAQ

What is a Bilateral Agreement in dual class?
The agreement between the two Classification Societies jointly classing a ship in dual/double class, defining survey responsibilities, sharing of outcomes, and handling of any class suspensions/withdrawals.
What is the 'Remaining Society'?
The Classification Society that keeps the ship in class when the other Society in the dual/double class agreement suspends or withdraws its own classification.
Does IACS Transfer of Class PR-1 also apply to dual class?
The PR-1 framework primarily governs the transfer of class between Societies, but its coordination principles are extended, with adaptations, to managing dual/multiple classification through the specific bilateral agreements.
🎬 Additional photos, videos and interactive diagrams for this topic will be available in a future version of the platform.

## Related Topics

Harmonized System of Survey and Certification (HSSC)Condition of Class and Recommendations

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