And before you mark everything Reconciled when you do Sept, 2017, be sure to look at the Oct., Nov., and possibly even Dec. to make sure there are not checks written in Aug. or Sept. that were not submitted until Oct. or possibly even later.

And if you find when you do Oct. and Nov. that they don't reconcile for some reason, remember you can UN Reconcile and start over.  Just make notes as to what didn't work the first time and leave those items open until you get to the appropriate month.