IHTM45002 | Reduced rate for gifts to charity: introduction and conditions: charitable giving condition or 10% test
From HM Revenue & Customs · Inheritance Tax Manual
The charitable giving condition is set out in IHTA84/Sch1A/Para 2(2). In order to qualify for the lower rate; the donated amount must be at least 10% of the baseline amount.
The ‘donated amount’ is defined in IHTA84/Sch1A/Para 4 as the amount of the component (IHTM45003) which is attributable to property that qualifies for charity exemption (IHTM11101). This could be a legacy of a specific amount, a share of the residue, or a share of the estate that is quantified (IHTM45003) so as to ensure the estate, or a component of the estate, will meet the 10% test.