Finish your 2015 return
First things first. If you received an extension to file back in April, finish up your 2015 tax return now.
Sure, you have until Oct. 17 (the usual 15th deadline is on Saturday) to get the forms to the IRS, but you don't have to wait until the last minute. Finishing up your taxes in a rush, whether in April or October, is a recipe for disaster.
At best, you could overlook a deduction or credit that could cut your tax bill. At worst, you could make a filing mistake that could undo all the tax work you got around to completing.
Remember, too, that the IRS' Free File program is still operational. If your adjusted gross income last year was $62,000 or less, you can use the online system to prepare and file your taxes for, as the name says, free.