OK. There are other ways to accomplish a change of fiscal year, but you'd want to be talking to your Adagio consultant.
Imports are fiddly. You are going to have to figure out why the debits and credits aren't equal. Try exporting and importing through and Excel sheet rather than through a CSV. Inspect the exported transactions to make sure all the ones you expected were exported.
Are you letting the import set the fiscal period, or are you setting the fiscal period in the import file? Do the debits and credits balance within each period?
Sorry, but this is about the limit of the guidance that can be provided on the Forum. Someone needs to be looking at your actual data and import/export templates.
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Andrew Bates