IHTM40051 | Is the application for clearance premature? : general
From HM Revenue & Customs · Inheritance Tax Manual
Sometimes the taxpayer will send in a form IHT30 before you are in a position to consider clearance. For example, you know that
If this happens you will have to decide if it is better to hold the form IHT30 on file or to return it to the taxpayer or agent for resubmission at a later date.
Outstanding penalty issues are not a reason for delaying giving clearance.