You are right, it should be 2004/06/30. I made the changes on the server when I was testing the query and I forgot to change it in the text...

Thanks for the replies. Looking at the suggestions given I end up with this query:

SELECT CUSTOMER, MONTH(DATEADD(DAY,DATE,'2004/07/01'))AS MONTH, YEAR(DATEADD(DAY, DATE,'2004/07/01'))AS YEAR, SUM (SALESAMOUNT) AS SALES

FROM MY_TABLE

GROUP BY MONTH(DATEADD(day,CDC,'2004/07/01')), YEAR(DATEADD(DAY,...