From ACT Wiki
In a commercial context, a customer is an individual or organisation that pays for goods, services, or both.
2. Public sector.
In relation to public sector activities, customers are the people or organisations that receive services provided by public sector bodies.
For example, the UK's tax authority HM Revenue & Customs (HMRC) writes: "HMRC is a high volume business; almost every UK individual and business is a direct customer of HMRC."