Invoicing depends on what your main business is. The current billing tax rates are 17%, 13%, 6% and 3%. Different industries have different tax rates. If your main business is information consulting, the tax rate is 6%, if not, it is 3% on a small scale. It depends on your specific business.
After the establishment of each company, whether there is tax or not, it is the responsibility of the enterprise to file tax returns on time.
You should find a professional accountant to handle tax returns, or you can find an agent to keep accounts.