Hi All,
I am very bad at formatting,please dont mine.Let me know if it works for you!!
SELECT
                          QL.USERAccounts
                         , QL.Accounttype
                         , QL.Billingcode
                         , QL.Rank
                         --, Ql.seq    
                        
                        FROM          
                          (SELECT
                                    USERAccounts
                                , Accounttype
                                , UA.BillingAccountKey
                                , BCR.Rank
                                , BCR.BillingCode
                                , ROW_NUMBER() OVER(PARTITION BY UserAccounts ORDER BY UserAccounts) as seq

                            FROM #UserAccount UA
                                                INNER JOIN #BillingTransactions BT ON UA.BillingAccountKey=BT.BillingAccountKey
                 
                                                INNER JOIN #BillingCodeRank  BCR ON BT.BillingCode=BCR.BillingCode    
                 
                            WHERE AccountType='O'
                            )AS QL

                        WHERE
                         seq=1
                        ORDER BY
                                  QL.UserAccounts