STSM031020 | Scope of Stamp Duty Reserve Tax (SDRT): territorial scope
From HM Revenue & Customs · Stamp Taxes on Shares Manual
While the scope of a charge to Stamp Duty Reserve Tax (SDRT) at the rate of 0.5% or 1.5% is restricted to ‘chargeable securities’ (as defined in FA86/S99(3), (4) & (10)) which are agreed to be transferred, the tax charge applies:
Irrespective of whether the agreement, transfer or appropriation of such chargeable securities is made or effected in the UK or elsewhere, and
Irrespective of whether any party to the agreement to transfer the chargeable securities is resident or situate in the UK.
STSM031090 gives more information on ‘chargeable securities’.