Bahá'í law of Zakát

Bahá'u'lláh states that the Bahá'í law of Zakát follows "what hath been revealed in the Qur'án" (Q&A 107). Since such issues as the limits for exemption, the categories of income concerned, the frequency of payments, and the scale of rates for the various categories of Zakát are not mentioned in the Qur'án, these matters will have to be set forth in the future by the Universal House of Justice. Shoghi Effendi has indicated that pending such legislation the believers should, according to their means and possibilities, make regular contributions to the Bahá'í Fund.

- Kitab-i-Aqdas

http://theaqdas.org/fullindex.php?term=future%20legislation&belongsTo=powers%20and%20duties;%20House%20of%20Justice,%20Universal%20(International)&level=3