Wa `alaykum As-Salamu wa Rahmatullahi wa Barakatuh.
In the Name of Allah, Most Gracious, Most Merciful.
All praise and thanks are due to Allah, and peace and blessings be upon His Messenger.
Dear brother in Islam, we would like to thank you for showing keenness on learning the teachings of Islam, and we appreciate the great confidence you have in us. We hope our efforts meet your expectations.
In Islam, zakah has its own special characteristics and special rulings. It is different from tax paid to governments. Hence, income tax doesn’t replace the zakah.
Responding to the question, Dr. Monzer Kahf, a prominent Muslim economist and counselor, states the following:
No, you are not allowed to do so, dear brother. Zakah is one of the pillars of Islam, and it is a religious obligation with given characteristics, qualification, intention, recipients, etc.
Are you are sure the religious authorities take 2.5% of your income as zakah? Taxes have different characteristics and uses. The least to your answer is that you are in a Muslim country, and the way your government handles these things indicate that they are quite different. How come you want to make them the same?
You can also read:
Taxation System: A Substitute for Zakah?
If you have any further questions, please don't hesitate to write back!
May Allah guide you to the straight path, and guide you to that which pleases Him, Amen.