As a principle Zakat is calculated on your Total Salary i.e. Zakat on Production = [(Monthly Salary of 100,000*12)-Nisab for Yearly Production Zakat]*10%
However, there can be difference of opinion on whether Zakat percentage (10% in your case) should be applied on amount only above Nisab threshold (as given in the equation above) or on the whole amount as soon as it crosses the Nisab threshold (i.e. Zakat on Production assuming total production to be greater than Nisab = [Monthly Salary of 100,000*12]*10%). Please see these responses of Ghamidi Sahab in this regard:
Discussion 988 • Reply 31187
Discussion 988 • Reply 36937
If there is no tax then one can use the nisab of amount equivalent to 653 kg of dates. Please see for details:
Discussion 48837
__
For Details on Law of Zakat, please see:
Discussion 58129 • Reply 58137