LAW 101: What are the Just Causes for Termination of Employment by the Employer?

An employer may terminate an employment for any of the following causes:

a) Serious misconduct or willful disobedience by the employee of the lawful orders of his employer or representative in connection with his work;
b) Gross and habitual neglect by the employee of his duties;
c) Fraud or willful breach by the employee of the trust reposed in him by his employer or duly authorized representative;
d) Commission of a crime or offense by the employee against the person of his employer or any immediate member of his family or his duly authorized representatives;
e) Other causes analogous to the foregoing;
f) Termination pursuant to a union shop/closed shop agreement in a CBA;
g) Defiance of an employee of a Return-to-Work order; and
h) Failure to meet the standards set in a probationary contract of employment.

Sources:
ART. 282, Labor Code of the Philippines;
See also http://www.dole.gov.ph/faq/details.asp