NIM16402 - Class 1A National Insurance contributions: Special Class 1A NICs cases: Workers going or coming from abroad who are provided with benefits: General conditions applying to liability for NICs - the employer
The Social Security (Categorisation of Earners) Regulations 1978 (Categorisation of Earners Regulations) (SI 1978 No 1689)
Section 1(6)(a) Social Security Contributions and Benefits Act 1992
In general, a person, normally the employer, is liable to pay NICs only if he is a liable secondary contributor. To be a liable secondary contributor an employer must be resident or present in, or have a place of business in the United Kingdom (UK) (UK means Great Britain and Northern Ireland) at the time liability for NICs arises.
In cases where an employer claims to have no place of business in the UK, the Categorisation of Earners Regulations may be applied so as to treat someone as a secondary contributor. Paragraph 9 of Schedule 3 to the Categorisation of Earners Regulations sets out the circumstances in which this treating provision is applied. More detailed guidance is available at NIM33023.
Section 1(6)(c) Social Security Contributions and Benefits Act 1992
A person may pay Class 1A NICs voluntarily if they wish, even if he does not satisfy the residency and presence conditions. Though unlikely to be offered, voluntary payment of Class 1A NICs can be accepted.