If I file for an extension but still have to pay by April 18,, how will I know what I owe?

[EricG1 · Accepted solution]

During the extension filing process, there is an estimation calculator that can tell you an estimation of how much you owe based on what form(s) you have to file. If it comes up 0, then you owe nothing. If it comes up with something else, you would pay that. And if you wind up overpaying/underpaying, the IRS will refund you or bill you when you file, based on the situation.