Any gain arising on the exercise of a share option is liable to income tax, USC and employee PRSI. There is no employer PRSI liability. There have been changes on how this is handled from 1st July 2012.
Income tax and USC arising on share option gains prior to 1st July 2012 was payable directly to the Collector General along with a form RTSO1 within 30 days of the exercise of the option. If the individual was still in the employment of the employer who granted the option, the employer was responsible for collecting employee PRSI through payroll. If the individual had ceased that employment, the individual was responsible for paying the PRSI to the PRSI Special Collections unit.
Since the 1st July 2012, the form RTSO1 has been amended to include employee PRSI. Hence, employee PRSI should now be returned to the Collector General along with the income tax and USC within 30 days of the exercise of the option and is no longer collected through payroll.