What does one row represent?
Specify whether a row represents an order, line item or payment. Joining different grains carelessly can inflate totals. Reconcile model totals against the source.
Separate facts and dimensions
Organising sales events as facts and dates, products and customers as dimensions clarifies filtering. Check unique keys, relationship direction and missing values separately.
Test the management question
When a month and branch are selected, do revenue and margin use consistent logic? How are returns handled? Manually reconcile small examples and document exceptions before approving visuals.