There is no problem in the late submission of the income certificate. You can submit your other necessary documents and regarding the income certificate you can ask for sometime for the late submission from the college admissions department. In the meantime you can get the certificate from the government official of your area and then submit it in the college.

yes you can submit it later on if you dont have any option to submit at the time of registeration. need not to worry you can submit it whever the commensment of classes occur. all the best.