CCPG26220 | Warning letter: considering whether to issue a warning letter: Customs Penalty Action Checklist
From HM Revenue & Customs · Customs Civil Penalties Guidance
You must complete a Customs Penalty Action Checklist (CPAC) to consider whether a Civil Penalty Warning Letter (CPWL) is the appropriate course of action.
The template is on SEES.
There is further guidance at CCPG26230 - CCPG26290 about the questions within the CPAC.