Use this reference to trace it from the Income Tax Ordinance 2001 (Part I of 2nd Scedule deal with Exemption from total income)
THE SECOND SCHEDULE (EXEMPTIONS AND TAX CONCESSIONS)
PART I (EXEMPTIONS FROM TOTAL INCOME)
Second Schedule_____Part-I_____(139) (a)
Any medical allowance received by an employee not exceeding ten per cent of the basic salary of the employee if free medical treatment or hospitalization or reimbursement of medical or hospitalization charges is not provided for in the terms of employment