Collect the complete scope
Identify participants, products, period and calculation rules. Establish which later agreement replaces an earlier term and which merely supplements it.
The last email may change one element rather than contain the whole arrangement. Keep an understandable summary with references to the supporting source agreements.
Identify the operative version
The summary needs an owner and confirmed scope. Resolve uncertainty before calculation rather than selecting the interpretation that produces a convenient result.
Record when changes apply. A new agreement should not automatically recalculate earlier transactions without a defined basis.
Update the shared record with each change
A correction should not remain only in the account owner's inbox. Planning, execution and settlement teams need the same applicable version.
For a commercial manager, this reduces differences between promises and calculations. Trade Marketing organises terms and documentation. The shared record helps when its approval and applicable scope are explicit, allowing another person to reconstruct the result without asking who remembers a particular message or relying on a private set of notes.