All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon our Prophet Mohammad and upon all his family and companions.
The father is obligated to provide for his children's needs, including food, clothing, shelter, and education if they don`t have wealth of their own. This obligation is based on the saying of the Prophet Mohammad (peace be upon him): "It is enough for a person to be considered sinful, that he neglects those whom he is responsible to sustain." [Abu Dawood]. In addition, failure to spend on one's dependents is considered neglect.
The father's financial support for his children should be done in a seemly manner. Imam Ibn al-Naqib, an Egyptian scholar, may Allah have mercy on him, said: "This financial support is determined according to sufficiency and is not considered a debt on the father, meaning that he isn`t liable for it with the passage of time" [Umdat al-Salik, p. 309].
The Jordanian Personal Status Law considers financial support (nafaqah) obligatory for the well-off father. The law specifies this obligation by requiring the father to cover the educational expenses of his children in all stages of education, including the preparatory year before the first grade, until the child obtains their first university degree, provided the child is eligible for education. This is outlined in Article 190 of the law: "The well-off father is obliged to bear the expenses of the education of his children in all educational stages, including the preparatory year before the first primary grade, until the child obtains the first university degree, provided that the child is eligible for learning."
Also, financial support is obligatory for the children according to their needs, and the father is not burdened with providing more than necessary. Sheikh al-Islam Imam Zakariya al-Ansari, may Allah have mercy on him, said: "There is no fixed amount for it, i.e., for the support of close relatives beyond sufficiency, as it is not determined except by need. It is obligatory as an act of compassion to meet their immediate need, so it is considered in proportion to the actual need and its estimation" [Asna al-Matalib fi Sharh Rawd al-Talib, Vol. 3/P.443].
The amount paid by the father for university fees must be spent on its intended purpose, and it is not permissible to use the excess amount without the father's knowledge. Taking someone else's money without right is considered unjust, as the wealth of a Muslim is not lawful to take except with his goodwill. The Prophet Mohammad, may peace be upon him, said: "Indeed, your blood, your property, and your honor are inviolable." {Reported by Muslim}.
In the context of a similar situation, it is mentioned in [Rawdat al-Talibin, Vol. 5/P. 368]: "He gave him... dirhams and said: Buy for yourself a turban or something similar. In the Fatawa al-Quffal, it is mentioned that if he said that in the usual context of casual giving, then it becomes his property, and he can spend it as he wishes. However, if the purpose was to collect what he specified, it is not permissible to spend it on something else."
In conclusion, if there is an excess amount from the university fees, the general rule according to Sharia is to use it for future credit hours or return it to the father. It is not permissible to dispose of the excess amount without his knowledge unless he allows it, in which case, it would be permissible. And Allah the Almighty knows best.