IHTM31019 | Assessing: calculation principles: withdrawing calculations
From HM Revenue & Customs · Inheritance Tax Manual
Usually, if the amount of tax charged has not changed, you should not withdraw the calculation. But, where:
there are agreed amendments to values, and
the calculations raised have not yet been paid,
the original calculations should be withdrawn. You should issue revised calculations, to include the new values.
You should not withdraw calculations in the circumstances shown at IHTM31020.