Government reports are intended to communicate with readers inside and outside government.
Reports are generally written in a reasonably formal style, but that does not mean they cannot be clear and easy to understand (see Clear and appropriate language for guidance on how to achieve a clear writing style).
Some regular reports will need to follow a particular format, with specified inclusions. For example, annual reports for government departments and agencies must follow the requirements of the Public Governance, Performance and Accountability Act 2013.