Professional Tax (PT) in India is a tax levied by the respective State Governments, and it's deducted from the income earned by employees. However, in the scenario you've described, where the full and final settlement has already been done, the PT deduction would typically not apply on the commissions being cleared a month later.
This is because the PT is generally applicable to the monthly gross income, and since the employee's full and final settlement has already been completed, they are technically not on the payroll in the month when the commission is being paid out.
However, it's important to note that this can vary based on specific state laws in India as the rules for PT deduction are not uniform across all states.
If the commission payment is substantial and could potentially change the PT slab for the employee for their last working month, it would be advisable to consult with a labor law expert or the local labor department to confirm how to proceed.
Remember, it's always better to err on the side of caution when it comes to taxation matters and labor laws.