Canceling EP and leaving in short notice

Hi all,
I have few questions need help:
1. How long does it take for EP cancellation? Does it really have to take one month?
2. If I have done tax clearance with previous company (but with CP21), and no income with current company, what should I do for tax clearance?
Thanks for helping out!

I've seen on the ESD website under Downloads section that it may be possible to cancel the EP without submitting passport to immigration. Don't know the ins and outs but requires some sort of affidavit or like