IHTM46025 | Calculating the RNRB: terms used: the 'adjusted allowance'
From HM Revenue & Customs · Inheritance Tax Manual
The legislation refers to a person’s ‘adjusted allowance’. This is the reduced maximum possible RNRB when the value of the estate exceeds the taper threshold. The adjusted allowance is calculated by deducting the amount of tapering from the ‘default allowance’ IHTM46023).