Taxpayers can use the official IRS website to find the appropriate mailing address for their state return; the address is different for individuals enclosing a tax payment versus those who are just mailing in their tax return. Some states require that specific tax forms be mailed to a different address.
Individuals who are mailing their tax returns need to make sure that the return is post-marked by April 15. The IRS considers a return post-marked by April 15 to be an on-time return. Those people who do not file their return on time are subject to a "failure to file penalty." If they owe money, they can receive a "failure to pay" penalty in addition to interest charges on their balance.