I have two client companies who are predominantly carrying out scientific research projects. I would like to know the details on the new research and development (R&D) tax relief restrictions put in place for overseas workers and contractors. 

Company A studies certain species that are not in the UK as part of their scientific research. The studies need to take place in the natural environment of the species as there are government restrictions for those species in the relevant state.

Company B carries out lab work which could but done in the UK, but the company chooses to engage overseas workers and sub-contractors as it is more efficient for the profits of the company.