What is professional tax and why is it deducted from salary?

Professional tax is a state-level direct tax generally deducted from the salaries of eligible employees and paid to the state government. Charged as a percentage of the income, it applies to individuals/entities engaged in a profession, trade or employment, with the annual tax capped at ₹2,500 under Article 276 of the Indian Constitution. However, not all states levy professional tax.