TSEM3042 | Trust income and gains: the charge on trustees - annuity as charge on trust
From HM Revenue & Customs · Trusts, Settlements and Estates Manual
An annuity is normally regarded as a charge on the trust income generally. See Trust & Estate return boxes 10.2A - 10.4A.
Sometimes an annuity is legally secured on the income of a particular part of the trust fund. If so, it is a charge on that income only.