You had only provided the gross salary; you did not furnish the Basic+DA details. If his Basic+DA is less than ₹10,000, then he is eligible for a bonus. If his Basic+DA is more than ₹10,000, then he is not eligible for the bonus, and you have to pay the bonus based on only Basic+DA, not on the gross salary. The minimum bonus is 8.33% of Basic+DA, and the maximum is 20% of Basic+DA.
For example, if an employee's Basic+DA is ₹7,500, then we have to calculate the bonus based on only ₹3,500. If his Basic+DA is less than ₹3,500, at that time, we have to consider the actual Basic+DA only.
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