Claim gratuity as an expense

Hi,

My client is a private limited company and he pays gratuity to employees to are eligible from his current revenue. they are nor members of any group gratuity fund. Is the payment made to any employee allowed as an expense in the year of actual payment. Considering that the amount is actually for the period of last five years before resignation and not of that year alone. Meaning no provisions have been made earlier.

Thanks in advance!

Hemali