NIM33325 | Special Cases: International: Going to or Coming from Abroad: EEA Regulation 1408/71 (before 1 May 2010): Posted Workers
From HM Revenue & Customs · National Insurance Manual
Note: This page is under review and the content may only be appropriate to periods beginning before 1 January 2021 and for those covered by a Withdrawal Agreement. A new International NICs manual is under development and will be published in due course.
Article 14.1(a) of Council Regulation 1408/71
A worker may remain insurable in the home State. The conditions that must be satisfied are
the employee is sent by the employer in the home State to undertake work for that employer in the host State
the work is expected to last less than 12 months at the outset
the worker is not replacing another employee who has completed a tour of duty abroad