A COE or Certificate of Employment is one of the requirements for pre-employment.
Under the Labor Code, “All workers who resigned or terminated from the company or establishment they were employed are entitled to certificates of employment.”
Section 10, Rule 14, Book 5 of the Labor Code states that a dismissed worker shall be entitled to receive, on request, a certificate from his/her employer specifying the dates of his/her engagement and termination and the type or types of work on which he/she was employed.

Please Note that Certificate of Employment is not a clearance or a WAIVER on the part of the employer to file legal action or potential claims against his former employee.
Most people are asking if he/she can get a Certificate of Employment for AWOL problem.  “AWOL” or “absence without leave” may be considered a ground for termination of employment. Even if the same is not clearly dealt with under your contract of employment, it may still be a basis for termination as it is provided for under Article 282 of the Labor Code. The provision states, “An employer may terminate an employment for any of the following causes: x x x (b) Gross and habitual neglect by the employee of his duties; x x x”
Yes, you can still get your COE but you need to be cleared by the company before you can request for a COE.
Sample Certificate of Employment: