Salary for the purpose of calculation of bonus should include all components as agreed as part of remuneration. There has been a practice of taking only Basic and DA (in case you do not pay DA, only Basic salary) for calculation of bonus. Therefore, if these travelling allowance, house rent allowance and medical allowance are fixed components which are paid without subject to any conditions, they should also form part of salary. The same treatment should be given with reference to deciding the eligibility for bonus. If you take gross salary for calculation of the amount of bonus payable, the same should be the salary for deciding whether the employee is eligible for bonus or not.
Madhu.T.K