§1. In addition to the offering mentioned in can. 1266, a bishop can impose a tax in the diocese to provide for the needs of the seminary.
§2. All ecclesiastical juridic persons, even private ones, which have a seat in the diocese are subject to the tax for the seminary unless they are sustained by alms alone or in fact have a college of students or teachers to promote the common good of the Church. A tax of this type must be general, in proportion to the revenues of those who are subject to it, and determined according to the needs of the seminary.
Source: Code of Canon Law (Vatican.va)