If one must give zakât but there is no official muslim authority, who checks if zakât is given?

First of all, I am not a muslim and thus do not know much about Islam, but I am reading a book from Tayeb CHOUIREF, *L'Islam expliqué* (Islam Explained, march 2022) and reached the part about zakât. Somewhere in the book, the author says that there is no official authority in Islam. By that, I mean any official, like the Pope for the christians, that gives orientation on how Islam should be practiced (not the corrects words, but I think you'll get the idea). This absence of authority is for all Islamic orientations but Shiite, if I remember well. However, when explaining what zakât is, the author says that it is given to poor people, or to *those responsible for collecting donations*. - Who is in charge of collecting it ? - How are these people selected ? - How do you make sure the collected donations are actually distributed to those needing it ?