The anniversary date is the day and month shown on the vessel's Certificate of Class, corresponding to the expiry date of the certificate. It serves as the reference date for scheduling the vessel's annual, intermediate, and special (renewal) surveys and for maintaining the validity of the ship's classification.

A Condition of Class (CoC), also referred to by some Classification Societies as a Recommendation, is a mandatory requirement issued by the Classification Society to rectify a defect or deficiency affecting the ship's hull, machinery, or equipment.

The required repairs or corrective actions must be completed within the specified time limit. Failure to clear the Condition of Class by the due date may result in the suspension or withdrawal of the vessel's class.

The window period is the specified time interval during which a periodic survey can be carried out without affecting the validity of the ship's classification.

For an Annual Survey, the survey is normally carried out within three months before or three months after the anniversary date. Completing the survey within this window ensures that the vessel's class remains valid and that the original anniversary date is retained.

Memoranda are informative notes or remarks entered by the Classification Society for the guidance of the Master, ship's staff, owners, or attending surveyors.

They are generally advisory in nature and do not require immediate corrective action. Memoranda may provide information regarding:

• Equipment limitations.
• Accepted structural deviations.
• Barred engine speed ranges.
• Other operational or structural information that should be noted during the vessel's service.

An Additional Note is a remark entered by the Classification Society to record special conditions or administrative information relating to the vessel.

It may include:

• Special classification notations granted to the ship.
• Compliance with voluntary or specific requirements.
• Administrative matters such as outstanding payments or registration-related information.
• Other conditions relevant to the ship's classification status.

A Statutory Recommendation is a requirement issued by the Classification Society while acting on behalf of the Flag State Administration under international conventions such as SOLAS, MARPOL, and other statutory regulations.

It specifies surveys, repairs, or corrective actions that must be completed within a prescribed time limit to maintain the validity of the vessel's statutory certificates. Failure to comply may result in the suspension or invalidation of the relevant statutory certification.