Mike:

You should open the new fiscal year 2018. You can have 2 fiscal years open at once. If you do that, your Retrievals from AP will go into the correct fiscal year. Not only that, you can have financial reporting for April 2017, May 2017 and June 2017. Adagio introduced the ability to have 2 years open simultaneously almost 10 years ago and to not use the feature is to make your life harder.

Once you have the new year open, highlight the AP batch in fiscal 2017 and click on the "Copy" button. Put check-marks on "Move", "Revise Period" and "Recalculate period based on date" then select "Next Year". This will move the batch to the "New Year" batch list.

Of course, this note assumes that you have a version of Ledger released in the past 10 years! If in doubt, post your Ledger version here.