How a computed column is created and why PERSISTED and storage go together: persisted columns take more space. Plus links to the whole series.
Computed Column Data Types: Why the Result Type Surprises You
Your table accepts every insert, then the report dies with an overflow error. Here is why the type is inherited and the cast that fixes it.
Readable IDs: A Bounded Computed Invoice Number
Create readable IDs with a computed invoice number while retaining the numeric key. Enforce the six-digit domain and plan format changes before growth.