Is not documenting the deferred dowry (mu’akhar as-sadaq) in the marriage contract, by choice, based on the saying of the Prophet, peace and blessings be upon him, "The best of women are those with the least mahr," and to avoid marriage fees, haram or halal?

The dowry (Mahr) is a right for the woman, which Allah has obligated for her. The father's waiving of his daughter's dowry without her consent is a matter of scholarly disagreement. It is not permissible according to the Hanbalis. According to the Malikis, a father may waive half of the dowry before consummation and after divorce. According to the Shafi'is, a guardian may not waive the dowry except under five conditions: that he be a father or grandfather, that the betrothed woman be a virgin, that the waiver be after divorce and before consummation, and that she be a minor or insane.

Based on this, if the non-inclusion of the deferred dowry (mu'akhkhar al-mahr) in the marriage certificate means waiving it for the husband, then this is not permissible and is not binding. However, if the non-inclusion does not imply a waiver, then there is no harm, but it is preferable to record it to avoid disputes.