What Letters should be taken while resigning?

While leaving the company, please do take a no dues certificate along with the copy of the relieving order, these two things are crucial for your future job search. Also, take a copy of the Form 16, it is also necessary to file your returns and also proof of your last drawn salary. Apart from that you need to take signature on the appropriate forms to transfer your P F if you are a subscriber  to transfer the P F account with the new employer. Other certificates like conduct etc... if issued by the company can be held by you on your records.