Of course. You can file anytime before the October 15th. window ( when the software shuts down). It is only that if you owe any monies to the tax authority ( IRS and/or the State), they may levy interest charges and sometimes penalty. By having an extension only thing you avoid is "failure to file" penalty but if you do not owe anything , then till Oct. 15th. there is really no major risk of that.
Just go ahead and file as soon as you can
