IHTM33013 | Loss on sale of land: disadvantageous claim
From HM Revenue & Customs · Inheritance Tax Manual
A claim following a sale at less than death value may not always be to the taxpayer’s advantage because
The taxpayer cannot withdraw a claim once it is made.
The taxpayer may try to make a claim following a sale at more than the date of death value even though it is clearly disadvantageous for Inheritance Tax purposes. Where this happens you should follow the instructions at IHTM33026.