At this point, you have no choice but to print, sign and mail your return to the IRS. If you paid on/before Apr 15th, then if your return shows you're getting a refund or owe nothing, then no late fees, interest or fines will be assessed and you're fine. But if that tax return shows you still owe the IRS (because you didn't pay enough by the Apr 15 deadline) then you will be assessed penalties, late filing fees and interest on the unpaid balance that was not paid before the Apr 15 payment deadline.