The VAT Return (Reports) builds the period's return from posted invoices only — the same population your VAT control accounts carry, which is the point. Choose the year and the month: the return shows output VAT (the tax on your sales) and input VAT (the tax on your purchases), each broken down by tax code, and the net: output minus input. Positive, it is VAT payable; negative, a refundable credit.
The return also cross-checks its figures against the VAT control accounts in the ledger. Agreement is the normal state, because both sides are written by the same postings; a disagreement means something reached the ledger without its documents, and finding it is a GL Statement (7.10) away. The return prepares the numbers — filing them with your tax authority, on their forms and their deadlines, remains yours.