Visit the official website of Professional Tax, i.e. http://pt.kar.nic.in, and click on 'Enrolment Application' on the left-hand side. A new page will appear, where you will have to select 'new' if this is your first time paying the tax, or 'enrolled' if you have filed the tax before. Type in the financial year, the professional tax office, the type of return, business status, and class of person. Then click Next.
You will then be prompted to enter other necessary details. You will need to make a payment in the final step. This can be done with a credit/debit card, or through net banking. You will receive a receipt once the payment is made, which you must download and keep for your records.