IRS Link to Form — Found Here
An individual can automatically have their tax return due date extended by 6 months by filing a Form 4868.
Tax returns are generally due by April 15, so this gives a person until October 15 to have the 1040 return submitted. This also goes for other tax return forms such as 1040-A and 1040-EZ.
Please note that the IRS expects your taxes to be paid by April 18th, using your best-guess at what you owe, in order to avoid additional charges. People often do not have their tax returns completed by April 15, for various reasons.
The IRS has made it easy to get an extension to get more time to file, by submitted a form 4868, which automatically increases the amount of time someone has to file by 6 months. The IRS still expects for tax money to be paid by April 18th, even if, after completing the return, it turns out you need to make adjustments to that amount and possibly get a refund.
The penalty for paying taxes late is .5% per month up to 25% unless someone can show a reasonable cause why the taxes were paid late. The IRS allows people to pay and file electronically these days, which can be relatively quick and painless.
For self-employed people, an extension may mean that they have until October 15 to make contributions to a SEP IRA for the previous calendar year, and the same might go for Traditional and Roth IRAs for others, although it could be that another extension form will need to accompany that contribution. For businesses and for other types of returns there will be different forms to apply for extensions.
The 4868 works for the 1040, 1040-A, and 1040-EZ.