If you fail to file either a tax extension or tax return by the appropriate filing deadline (March 16, 2015 for businesses and April 15, 2015 for individuals), the IRS will charge interest and penalties on any unpaid Federal taxes.f for any reason your tax extension is rejected, weâll tell you why, and you can resubmit for free after making any changes. Almost all rejections are caused by a Tax-ID not matching IRS records (caused by typos or change of filing information not on records with the IRS) .