SolvedCH179040 | Sanctionable conduct by tax advisers: how to process a penalty: enforcement of penalties
From HM Revenue & Customs · Compliance Handbook
All penalties must be paid
within 30 days from the date when we issue the notice of assessment, or
if the person appeals against the penalty, within 30 days beginning with the date when the appeal is withdrawn or determined.
These penalties may be enforced as if they are income tax charged in an assessment and due and payable.