NIC for posted workers from other countries
If you are sent to work in the UK from a ‘rest of world’ country by an employer in that country, you may not need to pay UK National Insurance contributions (NIC) for an initial period.
Migrants who are posted to the UK from a country outside of the EEA and Switzerland and with which the UK does not have a social security agreement, may not have to pay UK NIC for up to 52 weeks, provided they meet certain conditions. From 1 January 2021, these rules also apply to Liechtenstein. Broadly speaking you need to be employed overseas and then, as part of that overseas employment, you are seconded by your employer to work in the UK.
Migrants who do not meet the conditions will pay UK NIC from the start of their employment in the UK. This will include those who are locally employed in the UK.
For more information, go to HM Revenue & Customs’ (HMRC) guidance, RDR1, paragraphs 11.21 onwards. You can find this on GOV.UK.