Hi Mohit,
Salary certificate is not so important because you already discussed their salary and offered as per discussions. The important part is the resignation and acceptance letter. At times, what happens is that candidates negotiate their salary with the present employer while showing the offer letter, which is a very bad practice nowadays. Therefore, after giving the offer letter, ask immediately to send their resignation letter, and at the time of joining, tell them to come along with the acceptance letter.
As for the rest of the formalities, you have already got the answer.
Hope this helps you out.
Thanks,
John