Have you ever had asked about the status of a project you had assigned to someone only to be told it had been completed “some time ago?” Those who have had such conversations know the level of irritation you feel when you hear that response.
A project is not completed until it is reported completed. Full stop, no exceptions.
Why is this important? People act in reliance on information they receive. If they don’t receive information, they cannot act on it.
Think about this from the customer’s perspective, whether you are the customer and someone else in your perform is the “supplier,” or whether your client is the customer.