The NAO is based in London and Newcastle and has a staff of 800. Part of the NAO's London Office is a listed building, originally built for Imperial Airways as their ""Empire Terminal"". The building underwent a £60m restoration and refurbishment, completed in 2009. The NAO rents part of its offices to tenants, generating income of £1.1m in 2019–20.The building is a modern, open plan office and the refurbishment enabled the NAO to introduce many environmentally friendly features, such as rain-water harvesting.