Personal income tax is levied on your self-employed business management. The specific calculation method is more troublesome, so the state has issued a suggested calculation method, which is levied according to the business volume plus tax rate. This specific personal income tax rate varies from place to place. I can't give you the specific documents. But you can consult the local taxation bureau.

There is nothing wrong with this collection method.

I hope I can solve your doubts. If you don't understand, please ask.