CH411100 | Charging penalties: contract settlement: cases that need to be settled by contract
From HM Revenue & Customs · Compliance Handbook
Settlement by contract should continue to be used in cases where it is not practicable to assess the tax. The types of case that will still need to be settled by contract include
most EC and CIS cases because the formal process is normally more time-consuming
voluntary payments, for example EC employee benefits
complex cases of multi-entity non-compliance and contrived liquidations leading to a range of possible liabilities under IT, CT, PAYE, S419/S455
joint and several liability
companies that have been struck off
voluntary restitution cases.