VAT does not start when you open a return draft. It starts when you raise an invoice, record a supplier bill, capture an expense, or import bank activity that needs matching.
Sales side
When you invoice a customer, the VAT treatment on each line affects the output side of your return. If the coding is wrong at that point, the rest of the workflow becomes a repair exercise.
Purchase side
Bills and expenses matter because they support input VAT recovery where that recovery is allowed. Missing supplier evidence or unclear coding creates risk and wasted review time.
Reconciliation matters too
Bank matching does not calculate VAT by itself, but it helps you trust that the operational records and the money movement still line up. See how DII Accounts connects import, matching, and reporting.
Keep the workflow calm
If VAT feels difficult, it is often because the supporting records were never kept aligned in the first place. Start a workspace and keep the records tied together from the beginning.