Is it obligatory to differentiate between money and gold when determining the minimum taxable amount (nisab) for Zakat calculation, or is it obligatory to combine them?

Modern paper currencies have the same rulings as gold and silver regarding riba (usury), zakat (definition) (alms), and salam (forward contracts), as affirmed by the Islamic Fiqh Academy. Zakat is obligatory on banknotes if their value reaches the lower of the two nisab (definition) (minimum thresholds) for gold or silver, or if they complete the nisab when combined with other currencies or trade goods. The majority of scholars hold the view that gold and silver can be combined to complete the nisab due to their shared utility as monetary values. In contrast, the Shafi'is and some Hanbalis believe that each type of currency must independently reach its nisab.