Change the job with single permit

Hello guys,

I tried to search around but cannot actually find the answer or may be I missed it out.

I got a new job offer and they start applying a SP for me than they forward me an email seems from the Region that ask me a proof of termination in the past or in the future with the clear date and signed by my current employee.

I suppose it is correct to do so, don't it? Because sometimes I see that some people say they apply for the new job before quitting the current one to be sure so I'm not sure how to proceed now actually.

Thanks for your sharing!