Apologies, I missed a column from the GROUP BY:

SELECT DT.MO_OF_YR_NM [Month],

DT.MO_OF_YR[month_No],

DT.YR[Year],

DT.MIC_WK_OF_MO_NM [Week],

DT.DT [Date],

cstmr.[Organisation],

cstmr.CSTMR_KEY,

cstmr.CNTRCT_DD, -- NEW

PD.BS_LN_NM [Business Line],

ED.EMPE_NM [Sales Executive],

cstmr.[Total no of Lines],

[Total No Of Unpaid Lines] = CASE WHEN cstmr.[Total Amount Due] > 0 THEN cstmr.[Total no of Lines] ELSE 0 END,

cstmr.[Total Amount Due]

FROM DT_DIM DT

INNER JOIN (

SELECT

CDBF.FCT_DT_KEY,

[Organisation]= CD.CSTMR_NM,

cd.CSTMR_KEY,

[Total no of Lines] = COUNT(DISTINCT CDBF.CSTMR_KEY),

cdbf.ar_bhvr_key,

[Total Amount Due]= SUM(CDBF.BLNC),

CDBF.CNTRCT_DD -- NEW

FROM CSTMR_DUE_BLNC_FCT CDBF

INNER JOIN CSTMR_DIM CD

ON CD.CSTMR_KEY = CDBF.CSTMR_KEY --

GROUP BY

CDBF.FCT_DT_KEY,

CD.CSTMR_NM,

cd.CSTMR_KEY,

cdbf.AR_BHVR_KEY,

CDBF.CNTRCT_DD -- NEW

) cstmr ON DT.DT_KEY = cstmr.FCT_DT_KEY

Inner join AR_BHVR_DIM ABD

on ABD.AR_BHVR_KEY = cstmr.AR_BHVR_KEY

Inner join PD_DIM PD

on PD.PD_KEY = ABD.PD_KEY

Inner Join EMPE_DIM ED

ON ED.EMPE_KEY=ABD.EMPE_KEY

WHERE DT.DT>=@FromDate AND DT.DT<=@ToDate

/*

GROUP BY

DT.MO_OF_YR_NM,

DT.MO_OF_YR,

DT.MIC_WK_OF_MO_NM,

DT.DT,

DT.YR,

CD.CSTMR_NM,

PD.BS_LN_NM,

ED.EMPE_NM,

--CDBF.FCT_DT_KEY,

CDBF.AR_BHVR_KEY,

CDBF.CNTRCT_DD,

cd.CSTMR_KEY

*/

ORDER BY DT.MO_OF_YR

OPTION (EXPAND VIEWS)