Try this once
SELECT FDMSAccountNo
,Fee_Sequence_Number
,chargeback_amount
,[January],[February],[March],[April],[May],[June],[July],[August],[September],[October],[November],[December]
FROM (SELECT DISTINCT Fact_Fee_History.FDMSAccountNo,
--Fact_Financial_History.hst_merchnum,
Fact_Fee_History.Fee_Sequence_Number,
sum (Fact_Fee_History.Retail_amount) over(partition by Fact_Fee_History.FDMSAccountNo, Fee_Sequence_Number) as chargeback_amount,
DATENAME( Month, Month_end_date) Months
FROM Dim_Outlet INNER JOIN
Fact_Fee_History ON Dim_Outlet.FDMSAccountNo = Fact_Fee_History.FDMSAccountNo
WHERE Fee_Sequence_Number = '236'
and (Month_end_date >= @date)
and Dim_Outlet.MCC_Code in ('4814','4816','5967','7273','7841','7995','9754','9399','9754','5122','5912','5993')
) AS p
PIVOT
(COUNT(Fee_Sequence_Number) FOR Months IN ([January],[February],[March],[April],[May],[June],[July],[August],[September],[October],[November],[December]))AS pvt
--
Chandu