Overseas employee

My client has started a new venture.

One of the shareholder/directors is USA resident and domiciled

He is to be paid a significant (6 figure) salary on the payroll  .

His duties are to be performed outside the UK in developing overseas markets to exploit and networking with suppliers to establish facilities abroad, primarily USA and Canada.

There will be periodic visits to the UK for reporting purposes.

What is the payroll situation, i.e. is he exempt from NI and tax deductions, and if so does he need to apply anywhere for this?

Any help gratefully received