The poster himself has rightly quoted the maximum time limit for payment of bonus as fixed u/s 19(b) of the PB Act,1965.
Yet he raises a question whether it could be paid within the time in instalments as per the discretion of the employer.
A simple " YES " could be an answer as long as the employees agree to this. At times, some employers facing financial crunch resort to such a practice and the employees too accept it out of necessity and understanding. But, trying to make it a regular practice may sound unethical. As contemplated under the Act, bonus is a statutory payment based on the performance of the establishment in an accounting year. The main objective behind the arrangement is sharing the profit with the employee and not helping him on festive occasions. When the performance of the establishment is ascertained by balancing the books of accounts and basing on which the minimum or maximum amount of bonus is determined, in the absence of any valid reason for its disbursement in peace meal, such a proposal by the employer can not be appreciated, whether or not if objected to by the employees.