It's the law here !!
What is 13th Month Pay in the Philippines?
13th month pay in the Philippines is a statutory annual employee benefit that every employer is bound by Filipino law to provide to their full-time rank-and-file employees, in addition to their yearly salaries.
This benefit was legalized in 1975 by Presidential Decree No. 851 to support Filipinos and Filipino families through the Christmas period. Although the original legislation has undergone several amendments since it was first implemented, the fundamental framework of the law has remained the same.
Private sector employees covered by the 13th month pay in the Philippines benefit receive additional annual compensation on top of their annual salary. Every employee under the jurisdiction of Filipino law is entitled to it. This law provides an extra layer of safety net to all private-sector employees during the holiday season.