Secondments abroad contain financial risks for the home company. A secondment does not exclusively impact the employee and his administrative situation - the activity of the employee has also a direct impact on the taxes and social security of the home company.
Sending employees abroad might constitute a permanent establishment abroad, i.e. the Swiss entity becomes liable to income tax in the host country.
Every inbound assignee must be paid a salary that meets Swiss reference salary requirements for the time working in Switzerland. Thus, salaries currently paid in euro bear the risk to turn out to be too low and therefore not to be compliant anymore as a consequence of the decision of the SNB.