Article 431 of Civil Code

1 - If the creditor assigns his right to a third party and the debtor accepts the assignment without reservation, that debtor may not invoke against the assignee the set-off he could have invoked before accepting the assignment, and may only pursue his right against the assignor. 2 - If, however, the debtor has not accepted the assignment but has been served notice thereof, that assignment shall not prevent him from invoking set-off unless the right he wishes to set off arose against the assignor after Home Page 999 Law Index Civil Code Decree-Law No. 67 of 1980 AD Promulgating the Civil Code notice of the assignment.