Keep in mind that you have to provide a pretty good estimate of the tax amount you think you will owe when the full return is completed because you have to include that payment with the extension form. If the amount you send in with the form is less than the actual amount owed, you may have to pay interest and penalties on the additional amount owed.

You can find this form online at irs.gov, in many libraries and post offices, and if all else fails, call the IRS at its own toll free phone number and they can mail it to you.

The form itself is pretty straightforward. It asks for your name, address, and social security number. The tricky part is the tax estimate (line 4), and payments made (line 5). Instructions to the form guide you to which line of the tax forms (i.e. 1040, 1040A, EZ, etc.) correspond to this line of Form 4868. That's why I mentioned earlier that you have to do a pretty good estimate to file for the extension in the first place.

Line 5 is for you to calculate your total payments. Again, instructions to this form guide you to which line of the tax forms correspond to this line of Form 4868. Generally, it will be the sum of federal taxes withheld which are listed on W-2s from all employers, 1099 forms for bank interest, etc.

The difference between what you calculate as your estimated tax and payments already made will be the amount you remit ALONG with the form.

If you estimate an amount less than what you eventually calculate as the amount owed, you may be charged interest on that difference for the period of time between April 15 and when you actually pay, as well as a late payment penalty on the difference if the difference is more than 10% of your total tax liability which will also be calculated for the period of time between the regular April 15 due date and when you actually pay.

Finally, there may also be a late filing penalty (in addition to the late payment penalty) if your return is filed after the due date including extensions.

You have the ability to file via paper and mail the completed form and payment to the address included on the instructions depending on where you live, or you can file via Internet at irs.gov. Some tax preparation software and third party tax preparers may have software that also have the capability to file electronically. If you file via paper and mail, you'll pay via check or money order. If you file electronically, you'll pay via credit card or automatic debit of your bank account. Keep a record of this payment.

For more information, contact the IRS or an experienced financial advisor to see how your specific circumstances affect how you would fill out the form.