Start with the evidence
Retain the supplier source and ask the purchaser which work it supported. If the purchase served several projects, keep that question explicit for the responsible reviewer.
Work through the example
A USD90 printing receipt relates to materials for workshop PR-024. The purpose note and source link support the connection more clearly than an unexplained project code entered later.
Make the next step clear
Check the allocation through the established process and preserve its explanation. A convenient budget balance is not evidence that a cost belongs to that project.
Keep the source context
These guides are practical organizational examples for service and project teams. They do not promise a particular time-tracking, approval or project-management feature in Eftheia. Use the tools and controls actually available to your team.