Insert Validation:
Must be a valid AMS360 CompanyCode or WritingCompanyCode.
Update Validation:
Must be a valid AMS360 CompanyCode or WritingCompanyCode. Changes to WritingCompanyCode will result in an update for all LineOfBusiness and PolicyTransactionPremium rows for the policy term(includes policy effective date, past, current and future endorsement dates). WritingCompanyCode can be updated when IsCorrection is True. If billed or suspended billing exists an error message is returned.