If a person states his name differently during Nikaah so as to hide his real identity. This identity is falsely presented for a second marriage. Is this Nikaah valid ?

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

There are certain conditions for marriage to be valid, and once they are met, the marriage becomes valid. These conditions are listed in Fatwa 83629. These conditions include identifying the spouses. So, if the two contracting parties are distinguished by name, reference, qualities, or by any feature that distinguishes the husband and the wife in a way which makes them clear to the witnesses, then the identification required has taken place. Therefore, marriage becomes valid and the change of the name does not affect its validity.

Anyway, it should be noted that precautions must be taken (when concluding the marriage contract) in a manner that guarantees protection of the rights of others.

Allaah Knows best.