Asslam o Alaikum, I and my wife both have been working for last 10 years. and we both jointly have some wealth. which is well above nisab mashallah. we have disagreement on where to pay our zakat. so we want to pay separately. on what basis we calculate wealth share between us for the purpose of zakat calculation. JazakAllah
Both the husband and wife shall pay their Zakah on their respective wealth provided both are owner of Nisab separately. It is not considered when both wealth is combined together and it reaches up to the Nisab. If the wealth of none of them reaches up to Nisab separately then Zakah is not Fard upon them.
When you have joint wealth then you must add your share to your Zakatable assets and when that reaches Nisab then Zakat will be Fard.
الزكوة انما تجب اذاملك نصابا تاما ناميا حولاكاملا
(خلاصة الفتاوي ج.1ص.235,كتاب الزكوة,امجداكيدمي لاهور)
ويضم الذهب الي الفضة وعكسه بجامع الثمنية قيمة.....قوله قيمة أي من جهة القيمة فمن له مائة درهم وخمسة مثاقيل قيمتها مائة عليه زكاتها خلافا لهما
(الدرالمختارمع ردالمحتار ج.٢ص.٣٠٣،باب زكرة المال،سعيد)