You will need to adapt this to your specific needs, but you can try this:
The expression in the condition is the following. Replace triggerBody()['date'] with the dynamic date value that determines the fiscal year. It will return a number for the month. If it returns 1-8 it is the current fiscal year, otherwise it is the following fiscal year.
int(formatDateTime(triggerBody()['date'],'MM'))
For the folder path expression, use the following for the current year:
concat('/fiscalyear/', formatDateTime(triggerBody()['date'],'yyyy'))
Note: first use the folder picker to select the document library on your SharePoint site, and then paste that into the expression. For example, the document library I tested this on is 'fiscalyear'; be sure to include the backslashes.
For the next fiscal year, use this expression:
concat('/fiscalyear/', string(add(int(formatDateTime(triggerBody()['date'],'yyyy')),1)))
Again, do the same as above for the document library and folder path. This expression gets the current year and adds 1 to it.
