Va. Code § 15.2-417
The board shall require an annual audit of the books of every county officer who handles public funds to be made by an accountant who is not a regular officer or employee of the county and who is thoroughly qualified by training and experience. An audit by the Auditor of Public Accounts, under the provisions of law, may be considered as having satisfied the requirements of this section. The board may at any time order an examination or audit of the accounts of any officer or employee of the county government. Upon the death, resignation, removal or expiration of the term of any county officer, the board shall cause an audit and investigation of the accounts of such officer to be made. If, as a result of any such audit, an officer is found indebted to the county, the board shall proceed forthwith to collect such indebtedness.
Va. Code § 15.2-417