It depends on your relationship with bank. For some they need everytime for some they need once in a year, for some only email is sufficient, there are no fix rules in it, only main thing is that shipping bill set off must be done from banks, that is the most important thing. Because without set off export deal will not be completed in the eyes of banks and Government and your payment would be marked as Open.
After Setoff of Shipping Bill EBRC Would be issued to avail you benefits if any.