i live in california, and like the federal taxes we pay, we also pay state taxes, just like the IRS, the last day you can pay your taxes without getting penalties is the 15th of April.

one time, i forgot to send my income tax refund before the 15th and i was worried that i was not going to get my money back. but its the law, you have to get your money back and you dont get penalties if the IRS owes you money, only if you owe money to the IRS you get penalties.