Netherlands STAK (Stichting Administratiekantoor) and UK CGT on transfers

We have recently been approached to act for a client, a UK resident Dutch national, who several years ago, transferred significant investment assets to a Netherlands STAK (Stichting Administratiekantoor). At the same time, the client’s Netherlands resident mother transferred assets into the same STAK. The assets are held in a single portfolio and the two transferors were entitled to the underlying assets pro-rata based on contributions made.

Over the last few years, various capital gains and offshore income gains have been realised in the portfolio and the mother has periodically transferred lump sums of her entitlement to the underlying assets to our client.

I understand from HMRC’s international manuals that the STAK is treated as a fiscally transparent entity and that our client is taxed on her share of the underlying activity.

My question is: Are the assets transferred to the STAK by our UK resident client considered part-disposed to her mother for capital gains tax purposes at that date of transfer, with a corresponding acquisition of a share of the assets previously owned be her mother?

My thinking is that this is the case, we should view this transaction as if the STAK did not exist.

Tony Grubb