April 15 is the deadline for filing your tax return, and if you don’t think you will be ready, then get a four-month extension from the Internal Revenue Service.

But although the tax extension will give you extra time to get the paperwork to the IRS, it does not provide additional time to pay any taxes that are due.

You will owe interest on any amount not paid by the April 15 deadline, plus a late payment penalty if you have paid less than 90 percent of your total tax by that date.

Thus, you must make an accurate estimate of any tax due when you request an extension. You also may send a payment for the expected balance due, but it is not required to obtain the extension.

To receive an automatic extension, file Form 4868 with the IRS by Thursday, or make an extension-related electronic payment. You also can file your extension request by phone or by computer.

The IRS has a toll-free phone line for extensions, (888) 796-1074. Use Form 4868 as a worksheet to prepare for the call and have a copy of last year’s tax return.

You also may file an electronic extension request using tax preparation software on your computer or by going to a tax preparer. Those filing by computer get an acknowledgment that the IRS has received their request.

If your return is completed but you cannot pay the tax due, do not request an extension. File your return on time and pay as much as you can. The IRS will send you a bill or notice for the balance due.

You also may request an installment agreement by completing Form 9465 when you file the return or when you get the bill. The IRS will charge interest and penalties on the unpaid balance.