Can a company require an employee to pay the employer share of taxes (ie 12.4% for SS, 2.9% for Medicare) for options exercised? It does say in the paperwork that they will do so. If the options are exercised in January and the employee would have matched out at some point later in the year would this not be unfair to the employee as they are paying the 6.2% that would normally be part of the companies responsibility.