Legal analysis: the amount of special VAT invoice changes abnormally. Check whether the taxpayer's purchase and sale contract is true, check whether the taxpayer's production and operation are consistent with the signed contract, and check the inventory on the spot. Mainly check the inventory "raw materials" and "finished products" and monetary funds "bank deposits" and "cash" as well as accounts receivable and accounts received in advance. For the special invoices purchased in temporary increments, we should also focus on reviewing the performance of the contract.

Legal basis: Article 14 of People's Republic of China (PRC) Accounting Law includes original vouchers and accounting vouchers. To handle the economic and business matters listed in Article 10 of this Law, original vouchers must be filled in or obtained, and submitted to accounting institutions in time. Accounting institutions and accountants must examine the original vouchers in accordance with the provisions of the unified national accounting system, and have the right to reject untrue and illegal original vouchers and report to the person in charge of the unit; The original vouchers with inaccurate and incomplete records shall be returned in accordance with the provisions of the unified accounting system of the state and required to be corrected and supplemented. All the contents recorded in the original documents shall not be altered; If there is any mistake in the original voucher, the issuing unit shall reissue the certificate or correct it, and the correction place shall be stamped with the seal of the issuing unit. If there is an error in the amount of the original voucher, the issuing unit shall re-issue the L/C and shall not correct it on the original voucher. Accounting vouchers should be prepared according to the audited original vouchers and related materials.