What are the requirements of PER?

Please someone help me with this.

I am already done with 3 years of accounts related job (which also included some months as trainee in same office). Now i have left that job in Sep 2016 and my employer has issued me a experience certificate in which he has written about my role, my behavior etc.

I want to submit my PER. I know that I have to complete some PER questions and write about my performance which is not an problem. But I want to know that how does ACCA will verify my experience as accountant with my employer? Or just submitting experience letter and filling the PER objective is enough?

Sorry, if this question has been already answered, I have searched before writing and did not found any solution yet.