I have a dataset which lists the value at the end of each month.

I want to find the average of the month end total on annual basis

I can do that but it defines the year as Jan to Dec

Is there a way to tell Excel that the year start is April so it groups and averages on a April to March basis

Provide some sample data that is representative of your actual data as a downloaded file.

As you can see at How to Group Dates in Pivot Tables in Excel (by Years, Months, Weeks), you can define beginning and end of the period for grouping. If this does not work perhaps you do not have real dates ( left aligned in cell when NO manual alignment applies). then, by all means, follow Alan's suggestion

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