If it's past the April deadline, you may still be able to file your tax return. If you are due a refund, the IRS says that there is no penalty if you file a late tax return. However, if you owe tax, and you failed to file and pay on time, the IRS says that you “will most likely owe interest and penalties on the tax you pay late.”
Tax returns that are due a refund for withholding or estimated taxes must be filed within 3 years of the return due date to claim your refund.
If you cannot pay what you owe, you can request an additional 60-120 days to pay your account in full through the Online Payment Agreement application or by calling 1 (800) 829-1040.