From June 2025, HMRC will begin issuing Simple Assessment letters providing a detailed calculation for any tax owed by customers for income received between April 2024 and April 2025.

Simple Assessment letters should be to taxpayers who are not part of Self Assessment and who either do not have a PAYE tax code, or where tax cannot be automatically deducted through that process. The assessments are based on information which is already on the taxpayer's record, such as pension income or savings income based on previous years.

If a customer receives a Simple Assessment, but they have already registered for Self Assessment or filed their tax return for the year to which this assessment relates, they or their agent can call HMRC on 0300 200 3300 to have their Simple Assessment withdrawn.