can we process new joining without proper documentation

One employee is going to join in our company but he is not having proper document of last employer. I am having confusion how i will process his joining as he should submit all documents at the time of joining. but he is saying that he will not get any documents from his previous company.
please suggest me for the same.
previously i was taking new employee declaration regarding this but in this case he is not having any document excepting salary slip.
12th September 2019 From India, Pune

Hi,
It is employer specific. Some companies insist for proper relieving from past employer. In IT / ITES due to Project requirement due to project urgency many companies were not keen to collect it as it should not delay joining of new joinee.
12th September 2019 From India, Madras