SolvedCH64150 | Penalties for Failure to File on Time: How to process a penalty: What the assessment must include
From HM Revenue & Customs · Compliance Handbook
The penalty assessment must include
the date of the assessment,
the amount of the penalty,
the legislation under which the penalty is assessed, and
the tax period to which the penalty relates.
The penalty assessment also has a section explaining the appeal rights.
See CH62900+ if the outstanding return relates to a partnership.