Is professional tax a central tax, and what is the maximum an employee can be charged in a year?

Professional tax is levied by state governments, not the Centre, so the slabs, rates, registration and due dates differ from state to state, and a few states do not levy it at all.

The Constitution caps the amount a state can charge one person at ₹2,500 per year. Employers deduct it from salary under their state's slabs and deposit it with the state authority, usually monthly. Check your state's schedule before setting it up in payroll.