What is incumbent upon one who did not pay zakat for years, assuming that the nisab is calculated only with gold, then it became clear to him that his wealth reaches the nisab with silver?

If a Muslim possesses money that reaches the Zakat threshold (Nisab), which is equivalent to 85 grams of gold or 595 grams of silver, Zakat becomes obligatory on him after the completion of one full lunar year (Hawl). Given that banknotes are linked to gold and silver, scholars have differed on whether their Nisab should be calculated based on gold or silver, keeping in mind that the silver Nisab is more beneficial for the poor.

If you were unaware of the obligation of Zakat in past years, or if you were following a different jurisprudential opinion, then you are not required to make up Zakat for previous years, especially if the prevalent opinion in your country is to calculate the Nisab based on gold only, as is the case in Egypt, and is issued as a fatwa by many of their renowned scholars. Punishment is only incurred after the establishment of proof (Hujjah).