National Audit Office
From Longman Business DictionaryNational Audit OfficeˌNational ˈAudit ˌOffice abbreviation NAO nounACCOUNTINGORGANIZATIONS in Britain, a government organization that checks that government departments spend money correctlyA National Audit Office study found that the taxpayer could be losing £1 billion a year in housing benefit fraud.