What is the ruling regarding a deficit in the silver Nisab?
Chapter on Zakat on Gold and Silver
Al-Mughni
Book of Zakat
Primary text
If the Nisab falls short of the established measure, no Zakat is due, regardless of whether the deficit is significant or minor. This is the apparent view of Al-Khiraqi, the Madhhab of Al-Shafi'i, Ishaq, and Ibn Al-Mundhir, based on the explicit saying of the Prophet (PBUH), "There is no charity on less than five Ounces," where one Ounce is defined as forty Dirhams without dispute, equating to two hundred Dirhams.
Supporting text
Some scholars from our school (Hanbali) argue that if the deficit is slight, like one or two grains (Habbah), Zakat is still due because such minor shortages are not consistently preventable, resembling a short deficiency in the lunar year. However, if the shortage is obvious, like one or two Duwaniq, no Zakat is due. There is a narration from Ahmad that if the gold Nisab decreases by one-third of a Mithqal, Zakat remains due, a view held by Umar ibn Abd Al-Aziz and Sufyan; however, if it decreases by half, no Zakat is due. Another report from Ahmad states that if the reduction is in value (Thaman), no Zakat is due, a view favored by Abu Bakr. Imam Malik stated that if the reduction is a minor amount permissible in standard weighing, Zakat is due because it resembles the standard measure.