Praise be to Allah.
It is not permissible to give one’s mother zakaah that is the share of the poor and needy, because spending on her is obligatory upon her husband; if he is poor or refuses to spend on her, then her children must spend on her.
Ibn Qudaamah (may Allah have mercy on him) said in al-Mughni (2/279): If the poor woman has a husband who is well off, he should spend on her and it is not permissible to give zakaah to her, because she will have what is sufficient for her by means of what reaches her of that obligatory maintenance. If he does not spend on her and is unable to do so, it is permissible to give (zakaah) to her. This was stated by Ahmad.
End quote. For more information please see the answer to question no. 102755
If she does not have proper maintenance because her husband is poor or miserly, then her children are obliged to spend on her enough to suffice her, if they are able to do so.
Ibn Qudaamah (may Allah have mercy on him) said in al-Mughni, 2/269: Nothing of the obligatory charity (zakaah) should be given to one’s parents or children. Ibn al-Mundhir said: The scholars are unanimously agreed that it is not permissible to give zakaah to one’s parents when the one who is responsible for their maintenance is obliged to spend on them, and giving zakaah to them will mean that they no longer need this maintenance, in which case maintenance would be waived in such as way that he will benefit from that, and it is as if he gave the zakaah to himself.
But if they are not able to spend on her, then it is permissible to give zakaah to her, because it is not obligatory for them to spend on her in that case.
Shaykh al-Islam Ibn Taymiyyah (may Allah have mercy on him) said: It is permissible to give zakaah to one’s parents and grandparents, no matter how far the line of ascent reaches, and to one’s children and grandchildren, no matter how far the line of descent reaches, if they are poor and he is unable to spend on their maintenance.
End quote from Majmoo‘ al-Fataawa, 5/373. See also: ash-Sharh al-Mumti‘, 6/92; and the answer to question no. 85088
It is also permissible to give zakaah to the mother under a category other than that of the poor and needy, such as debtors, because it is not obligatory for him to pay off his mother’s debt, so it is permissible to give her zakaah in order to pay off her debts with it; rather she is more entitled to that. For more details please see the answer to question no. 39175.
And Allah knows best.