INTM332670 - Double Taxation applications & claims: permanent establishment and special relationship: What Special Relationship is
Special Relationship is a condition for relief you will have to consider when you give relief under some of the articles of a DTA.
If, because of a 鈥榮pecial relationship鈥� between the payer and the payee, a contract has been agreed on anything but 鈥渁rms length terms鈥� (see INTM431030) any relief from UK tax may be restricted or may not be available at all.