Use COALESCE or ISNULL function for each column which is nullable - for example like this:CONVERT( DECIMAL(10, 0), ROUND( (COALESCE(BASE_PREM,0) + COALESCE(PHYS_TMB_PREM,0)) * (1.0 + COALESCE(GROUP_DISC,0) / 100.0) * (1.0 + COALESCE(DISCOUNT_2,0) / 100.0) * (1.0 + COALESCE(EXPER_DISC,0) / 100.0) * (1.0 + COALESCE(RISK_MGMT,0) / 100.0) * (COALESCE(DISCOUNT_1,0) / 100.0), 0 ) ) AS IPA_MEMBER_PERCENT_DISC_AMOUNT
COALESCE or ISNULL returns the first parameter if that is not null, and if it is, then it returns the second parameter.