Try like this
Current Year and Current Month Exp:
sum({$<Year={$(=Max(Year))},Month={ "<=$(max({<Year={$(=Max(Year))}>} Month))>$(Max({<Year={$(=Max(Year))}>}Month)-1)"}>}
Last Year and Current Month Exp:
sum({$<Year={$(=Max(Year-1))},Month={"<=$(Max({<Year={$(=Max(Year))}>}Month))>$(Max({<Year={$(Max(Year))}>}Month)-1)"}>}
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For Current Year :
Sum({<year= {$(=max(Year))}>}Sales)
For Previous Year :
Sum({<Year= {$(= max(Year-1))}>}Sales)
