Should Zakat be paid on the highest value of money or on its lowest value if the money fluctuates between increase and decrease during the year?

The standard for the nisab (definition) (minimum amount subject to zakat (definition)) for money is the equivalent of 85 grams of gold. So, whoever possesses this amount or more, and a full lunar year (hawl) passes over it, must pay two and a half percent (2.5%), which is one-quarter of one-tenth. If another year passes and the amount falls below the equivalent of 85 grams, then no zakat is due until it reaches that amount again. Zakat is obligatory on the amount of money a person possesses at the time it becomes due, when the hawl completes, not on the amount he had previously.