Around 1.8 million Simple Assessment letters will be sent for the 2025/26 tax year, with working-age taxpayers already beginning to receive them. Why have I received a Simple Assessment letter? Myrtle Lloyd, HMRC's Chief Customer Officer, said: "If you receive a Simple Assessment letter and have tax to pay, please don't ignore it. "If you need extra support, or want to find out more, search 'Simple Assessment' on GOV.UK." Simple Assessment letters are official HMRC correspondence and are sent either by post or through a customer's Personal Tax Account.