<prompt> Human: How am I supposed to have ANY idea what I owe or if I owe without doing may taxes? Im filling the extension to get the time to actually work through a very complicated, multi-state, multi business, mess of tax information. Can I just say 0 and make up the difference later? So much has changed since last year, my previous taxes are probably not a good indication of anything.  <response>: An extension to file is not an extension to pay. If you end up owing money when you do eventually get around to filing, you will be charged penalties for that. Theyre asking you for your estimated tax burden now so that you have the opportunity to pre-pay any difference now so that you avoid those feesinterest. 