What should the questioner's relative do who owns gold that her husband does not declare, and who finds it difficult to pay its annual zakat due to deteriorating economic conditions? And should the value of the zakat be paid according to the price of gold at the time it becomes due or at the time of payment?

The gold saved by your relative, if it is for adornment, then there is no Zakat (definition) on it as long as she does not wear it for fear that her husband might sell it. However, if it was purchased not for the purpose of adornment, then Zakat is obligatory on it. The original principle is to pay Zakat from the gold itself, but it is permissible to pay it in cash.

Zakat becomes obligatory if the weight of the gold reaches 85 grams or more, and its amount is a quarter of a tenth (2.5%). If cash is not available, a portion of the gold can be sold to pay Zakat, and if that is not possible, there is no harm in delaying until money becomes available.

What is obligatory is to pay the value of Zakat at the time of its payment, not at the time the hawl (one lunar year) is completed. So, if the price of gold increases, the value of the obligatory Zakat increases.