How long is an extension of taxes?

It depends on the type of tax, but for personal income taxes - an automatic 6 month extension of when to file is easily available. NOTE; NO EXTESNION OF WHEN TO PAY IS AVAILABLE..YOU MUST HAVE PAID ON TIME AND UP TO THE CORRECT AMOUNT, or face substantial penalties and interest. This form, (read the easy instructions about it too) is all you need: http://www.irs.gov/pub/irs-pdf/f4868.pdf