OT28620 | Decommissioning and abandonment: decommissioning security agreements: tax treatment of sums paid out to meet the costs of decommissioning
From HM Revenue & Customs · Oil Taxation Manual
Relief for decommissioning costs will be due to the company when decommissioning costs are met from monies held by the trust.
The reasoning is that, as a matter of tax law, there is no out and out alienation of the monies paid into the fund as the company has a continuing beneficial interest in the fund.