There is a "workaround":

SELECT DV.[Year],

SOH.SalesPersonID,

AverageOrderAmt = SUM(SOH.TotalDue)

FROM Sales.SalesOrderHeader SOH

CROSS

APPLY (SELECT DATEPART(yyyy,OrderDate)) DV ([Year])

GROUP BY

DV.[Year],

SOH.SalesPersonID

ORDER BY

DV.[Year] ;

Over to you, Hugo.

Paul