If you have the idCAT issued with NIE and you obtain the NIF, you should go to an idCAT Registration Entity to request the revocation and re-issuance of your certificate. If you do not do so, your idCAT will contain erroneous data, as your legal identification document would be the NIF. In fact, when you try to process with the administration, you will get an identification error. To cancel the previous certificate and obtain a new one, you must provide the civil registry certificate stating the previous document and the new one, as well as the new NIF.