Residence: non-resident companies: distributions received
You should check the other guidance available on GOV.UK from HMRC as Brexit updates to those pages are being prioritised before manuals.
UK company distributions received by non-resident companies do not constitute franked investment income (see CTM34230) and are specifically excluded from the income of a branch or agency (see (b) of CTM34210). In principle, they are within the charge to IT but ITTOIA05/S399 (2) - qualifying distributions received by persons not entitled to tax credits, and ITTOIA05/S400 - non qualifying distributions, provide that income tax is treated as having been paid at the dividend ordinary rate and hence there is no liability
As regards cases covered by Double Taxation Agreements see INTM153110.