If you cannot pay the full amount of taxes you owe by due date includng the extension deadline, you should still file your return on time and pay as much as you can to avoid penalties and interest.
The IRS offers taxpayers alternative payment options and you should consider these options: Pay by Credit Card
You can charge your taxes on your American Express, MasterCard, Visa or Discover cards. To pay by credit card, contact one of the service providers at its telephone number or Web site listed below and follow the instructions. The service providers charge a convenience fee based on the amount you are paying. Do not add the convenience fee to your tax payment. Here are the sources and website for the service providers.
* Link2Gov Corporation: 888-PAY-1040 (888-729-1040)www.pay1040.com
* Official Payments Corporation: 800-2PAY-TAX (800-272-9829), or you visit www.officialpayments.com Requesting an Extension of Time to Pay
Taxpayers can request a n extension of time to pay the tax liability. The IRS is willing to allow extensions of time to pay in order to assist in tax debt repayment. The taxpayer could request a short term extension of time to pay through the Online Payment Agreement application at IRS.gov or by calling 1-800-829-1040. Taxpayers qualifying for an extension of time to pay of 30 -120 days generally will pay less in penalties and interest than if the debt were repaid through an installment agreement. Requestingt an Installment Agreement
The IRS may allow you to pay any remaining balance in monthly installments through an installment agreement. You can apply for an IRS installment agreement using our Web-based Online Payment Agreement application on IRS.gov.
The Taxpayer could also "attach a Form 9465, Installment Agreement Request, to the front of your tax return". The IRS charges a $105 fee for setting up an installment agreement. The fee is only $52 if you pay via direct debit. If your income is below a certain level (see Form 13844), you may qualify for a $43 fee.
The IRS states that "In most circumstances, the Online Payment Agreement application provides immediate notification regarding the approval of your request".