Use data validation lists

I need data validation lists deployed across the budget workbook so managers can only pick approved expense categories. On the Categories sheet create a single canonical list, then apply drop-downs to the Expense Type column on each department sheet. Ensure the lists allow only valid choices, show a custom error message explaining the allowed values, and update the validation if the master list changes.

Before I roll this out to department leads, make the validation easy to maintain. Move the master category list to a clearly named sheet, use structured references or named ranges so additions appear in every drop-down automatically, and add a short cell note explaining the purpose. Also surface any cells already containing invalid entries so leads can reconcile them quickly.

I added a new expense category last week but the managers’ drop-downs don’t show it, and some sheets now have free-text entries. I’m worried the validation was set up inconsistently. I don’t know which department sheets use static ranges versus the master list. What’s the fastest way to find all validations that aren’t linked to the master list and repair them without losing current data entries?

We keep spending time recreating drop-downs and cleaning free-text entries every quarter. I want to stop that churn and keep validation current as categories evolve. What process changes and simple governance will make the master list the single source of truth and prevent ad hoc lists from reappearing?