As I understand it the tax relief is available to employee on the gross which should appear on the payslip. It's the employee who receives the tax relief. Tax relief on VHI paid on behalf of employees is not available to employers.
1.2 BIK Medical Insurance credit Tax relief on medical insurance is granted at source on all premiums. Where an employer pays medical insurance as a benefit-In-kind [BIK], the employer pays the lower premium and repays the tax credit to Revenue through the Corporation Tax return/payment. The employee, whose medical insurance has been paid by the employer, must then claim the tax credit individually. To encourage employees who are taxed on the BIK to claim the appropriate tax credit, the P35 form for 2007 will include a new field to allow employers to notify Revenue of the amount of medical insurance paid as a BIK. Revenue will process this information and grant the appropriate tax credit to the individual employee in 2008