For some reason we see people afraid of filing an extension with the IRS to file their tax return.  For some reason, people think they are sending in the return late or that it raises a red flag with the IRS, which is not the case.  Although estimated taxes are due by April 15th, it is much better to file the extension and get the return correct than rushing to get it in.  You can get an automatic extension by filing form 4868 here.  So if you have received that last minute revised 1099 or K1, take a deep breath and remember you have another six months to file the return.