Legal analysis: proof of income is a kind of proof of economic income that China citizens need in their daily production, life and business activities. Generally, when handling visas, bank loans, credit cards, etc. They will be required to be issued by the relevant units. Self-employed individuals can't issue their own income certificates, but need street, industrial and commercial bureau or tax bureau to issue income certificates. It is a useful supplement to the socialist public ownership economy to give priority to individual workers and their family members, engage in production and business activities independently with their own means of production and funds, and provide goods and services to the society. The state protects the legitimate rights and interests of the individual economy. The state guides, helps and supervises individual operators through administrative management. In real life, self-employed people are generally engaged in various repair services, garment processing industry, cottage industry, individual transport industry, catering commodities and other productive and service industries permitted by policies. The tax authorities that have approved the collection generally implement a regular quota method for individual industrial and commercial households, that is, according to the area, location, area, equipment and other quota collection. They will give you a month's tax payable. If the invoiced amount is less than the quota, the tax shall be paid according to the quota; If the invoice amount exceeds the quota, tax shall be paid according to regulations. Those who fail to reach the threshold of value-added tax may be exempted from value-added tax, urban construction tax and education surcharge.

Legal basis: Article 5 of the Civil Law of People's Republic of China (PRC) stipulates that civil subjects should follow the principle of voluntariness and establish, change and terminate civil legal relations according to their own wishes.