Dear Chanda,
As this case appears to be different from others, where the employer pays bonuses based on productivity calculations, possibly as part of a contract or a general understanding between the employer and employees, the bonus percentage can be increased, fixed by agreement. You mentioned an Executive HR being paid 25%, while Managers receive up to 50%. In such cases, you may refer to the below section of the Payment of Bonus Act 1965:
31-A. Special provision with respect to payment of bonus linked with production or productivity - Notwithstanding anything contained in this Act, -
(i) Where an agreement or settlement has been made by employees with their employer before the commencement of the Payment of Bonus (Amendment) Act, 1976 (23 of 1976), or
(ii) Where employees enter into any agreement with their employer after such commencement,
For payment of an annual bonus linked with production or productivity in lieu of bonus based on profits payable under this Act, then, such employees shall be entitled to receive the bonus due to them under such agreement or settlement, as the case may be:
(Note: Ins. by Act 66 of 1980, (w.e.f. 21st August, 1980)) Provided that any agreement or settlement where employees relinquish their right to receive the minimum bonus under Sec.10 shall be null and void insofar as it purports to deprive them of such right:
(Note: Subs. by ibid) Provided further that such employees shall not be entitled to be paid such a bonus in excess of twenty percent of the salary or wage earned by them during the relevant accounting year.
Please let me know if this matter still seems confusing; we will strive for the best result.