Section 259BF | Meaning of “permanent establishment”
From legislation.gov.uk
(1)In this Part “permanent establishment” means anything that is—
(a)a permanent establishment of a company within the meaning of the Corporation Tax Acts (see section 1119 of CTA 2010), or
(b)within any similar concept under the law of a territory outside the United Kingdom.
(2)A concept is not outside the scope of subsection (1)(b) by reason only that it is not based on Article 5 of a Model Tax Convention on Income and Capital published by the Organisation for Economic Cooperation and Development.