Identify the factual basis and appropriate supporting records. Do not imply the manager personally observed events they know only through company records or others.
Separate sources of knowledge
Explain who can verify the relevant project and what the records show. Preserve dates and the applicant’s actual contribution. A change of manager is a reason to clarify evidence, not to invent a firsthand account.
Hypothetical example: an immunoassay validation scientist completed a transfer of methods to a partner site before the current manager joined, and the manager is asked to describe it. Two honest forms are available. The manager can write from the records, naming them, or a colleague who was present can provide a short separate statement of what they observed, with the manager’s letter covering the company facts they can verify directly.
Both are stronger than one confident letter that quietly implies presence at events. Build a small index for the file: for each significant assertion, the record that supports it, the system it lives in and the person who maintains that system. Where a record has been destroyed under a retention schedule, say so and name the schedule, because a documented gap reads very differently from an unexplained one.
An index of that kind also shortens any later request for evidence. Name the retention schedule by its internal title so the reference can be checked.