Re: HMRC referring to taxpayers as 'Customers'
"I thought that customers meant the other Government Departments."
HMRC refer to taxpayers as customers.
http://www.express.co.uk/news/uk/693767/hmrc-calls-taxpayers-customers
https://www.accountingweb.co.uk/tax/hmrc-policy/stop-calling-us-customers-taxation-campaign
..and from their own spiele:
"are a high volume business; almost every UK individual and business is a direct customer of HMRC"
https://www.gov.uk/government/organisations/hm-revenue-customs/about