Vat Audit........
Ensure that you have all records for the period in question.
These include,
Bank Statements (Details of lodgements, Cheque book anaylsis.)
Purchase Invoices
Sales Records
Sales Receipts
Copies of Vat returns and supportign schedules showing how the final liability or refund was arrived at.
Not advised: But in the practice I work in we put the revenue auditor in a cold filing room, what normally happens is that he/she doesnt stay too long, rushes over his/her checks etc, and ends up taking some the records with them for final checks.
If you have prepared for vat in the correct way then there shouldnt be any problems.