When You Owe
If you owe money back to the IRS, you are expected to pay the amount due in full when you file your taxes. The paperwork and money must be sent in by the April 15 date. Keep in mind that if you miss that deadline, the amount you owe will increase as a result of penalties and interest that is accrued for being late. (See “The Cost of Being Late” section below for more details on this.)
You can pay your income taxes through several approved methods. For instance, you can use the U.S. Department of Treasury’s Electronic Federal Tax Payment System (EFTPS) to electronically transfer money from your bank account. You can also pay via credit card through the Official Payments website or Pay1040. Both of these vendors are approved by the IRS for this purpose.
If you prefer to send a personal or cashier’s check or money order, the funds should be made payable to the United States Treasury. Also be sure to include the necessary information on the check, such as your social security number or employer identification number, tax period, and the associated tax form number.
If you prefer to pay in cash, you can do this in person through a local IRS branch.
When You Can’t Pay In Full
If you can’t afford to pay the full amount you owe in income tax, you should still file your paperwork by the date it is due and explain your personal situation to an IRS representative to find out what your options are. For instance, you may be able to pay a portion 
of the amount due and then arrange an installment or payment plan for the balance. You could also request an extension. In certain cases, the IRS may even agree to a temporary delay or consideration of a significant hardship. It is important to note, though, that the federal government has the right to file a tax lien against you until you have settled your bill. Finally, if there is a question of whether your bill is correct, or whether you will ever be able to pay the full amount, you may be able to arrange a compromise on the total due. However, if you do agree on a compromise and then default on the negotiated amount, the IRS can sue you and come after you for what the amount you had originally owed, plus accrued interest and penalties, too.