Legal analysis: 1. The purchase invoice of agricultural products is only used when the purchasing unit purchases the duty-free agricultural products listed in the Notes on the Scope of Taxation of Agricultural Products from individual agricultural producers. 3. The purchase invoice price is the actual purchase price of agricultural products paid to agricultural producers. 4. If the payment is made in cash, the payee shall sign the purchase invoice;

Legal basis: Provisional Regulations of People's Republic of China (PRC) on Value-added Tax.

Article 15 The following items shall be exempted from value-added tax:

(1) Self-produced agricultural products sold by agricultural producers;

(2) Contraceptive drugs and devices;

(3) old books;

(4) Imported instruments and equipment directly used for scientific research, scientific experiments and teaching;

(5) Imported materials and equipment provided free of charge by foreign governments and international organizations;

(six) articles for the disabled directly imported by organizations for the disabled;

(7) selling articles for personal use.

In addition to the provisions of the preceding paragraph, the items of tax exemption and reduction of value-added tax shall be stipulated by the State Council. No region or department may stipulate tax exemption or reduction items.

Article 16 Where a taxpayer concurrently engages in tax exemption or reduction projects, it shall separately account for the sales of tax exemption or reduction projects; If the sales volume is not accounted for separately, no tax reduction or exemption shall be allowed.