Axa Isle of Man is to go up against HM Revenue and Customs before the Special Commissioners later this month.
The case, which is being heard on October 18 and 19, is the culmination of a long-running disagreement between the insurer and HMRC over whether its estate planning bond can be sold to clients aged over 90.
The case was originally expected to be heard by the Special Commissioners last year and the judgment from the delayed hearing is not expected to be delivered for around six to eight weeks.
The case revolves around a technical issue over whether discounted gift trusts like the estate planning bond are effective if taken out by an individual aged over 90.
HMRC argues there is no market to buy the income stream from the trust so it has no resale value. It says any buyer would want to protect their income stream by buying a life insurance policy but over-90s are uninsurable. Axa will dispute this argument.