You can register as a self-employed person in the "My Tax" mobile application of the Federal Tax Service of Russia or in the taxpayer’s account "MY TAX".
You can deregister yourself as an income tax payer at any time in the taxpayer’s account "MY TAX" or in the "My Tax" mobile application of the Federal Tax Service of Russia.
It is possible, in this case, the employer will pay your personal income tax in the amount of 13%, and you will pay a tax on professional activities in the amount of 4-6%.
The tax is paid up to the 25th day of each month following the expiration of the tax period (calendar month), except for the period from the date of registration (+ 1 month).
For more detailed information on the tax regime on professional income, please, visit the website of the Federal Tax Service of Russia https://npd.nalog.ru/faq/