Permissible if conducted before the husband and wife meet each other.
Darul-uloom Banuri Town (Karachi):
Permissible according to some Scholars of knowledge and legally valid before the husband and wife meet each other.
Shaykh (Mufti) Hussain Kadodia (HA):
In order for the Walimah to be valid, it must be held after the couple "consumate" the marriage. This would take place by them being in privacy for a few minutes. The sunnah practice was that the walimah would be held the day after the marriage, however if one does have it on the same night- after the couple spend time together in privacy- it would be ok, especially as, nowadays having it the next day leads to a host of other expenses, the incurring of which is completely contrary to the spirit and sunnah of marriage.
