The Jizya is only upon capable males. Imam Ibn Qayyim writes;
“There is no Jizya on the kids, women and the insane. This is the view of the four imams. Ibn Munzar said, ‘I do not know anyone to have differed with them.’ Abu Muhammad ibn Qudama said in al-Mughni, ‘We do not know of any difference of opinion among the learned on this issue.” (Ahkam Ahl Zimma 1/14)
“And there is no Jizya upon the aged, one suffering from chronic disease, the blind, and the patient who has no hope of recovery and has despaired of his health, even if they have enough.” (Ahkam Ahl Zimma 1/16)
One important incident quoted by Imam Abu Yusuf needs special mention;
‘Umar bin Khattab, may Allah be pleased with him, passed by the door of a people’s dwelling. There was beggar there saying, “Extremely old person with blind eyesight [needs help!”] He [‘Umar] got hold of him from behind and asked, “Which community of the People of Book you belong to?” He said, “I am a Jew.” He asked, “What brought you to this condition that I see?” He said, “The demand of Jizya, the needs and the old age.” ‘Umar got hold of his hand and brought him to his place helped him a little and then called for the custodian of Baytul Mal and said, “Take a look at his suffering. By Allah this is not justice on our part that we extract from them in their youth and leave them helpless in their old age! … He exempted him from Jizya and similarly the likes of him. (Kitabul Kharaj 1/139)
Orientalist, Thomas Armold puts it as;
“The tax was to be levied only on able-bodied males, and not on women or children. The poor who were dependent for their livelihood on alms and the aged poor who were incapable of work were also specially excepted, as also the blind, the lame, the incurables and the insane, unless they happened to be men of wealth; this same condition applied to priests and monks, who were exempt if dependent on the arms of the rich, but had to pay it if they were well-to-do and lived in comfort. The collectors of the jizyah were particularly instructed to show leniency, and refrain from all harsh treatment or the infliction of corporal punishment, in case of non-payment.” (The Preaching of Islam p.60)