If by Big 4 you mean Deloitte, forget about it. It's a separate company in each country. It's hard enough to get a "transfer" (=new contract) as an existing employee, never mind as a new hire, and it certainly isn't within the gift of HR. In any case, they really just administer, rather than make the hiring decision - after all, it's not money going out of their cost centre.Some or possibly all of the above is likely to apply to other firms, too.