Legal analysis: illegal. 1. Invoice can be used as reimbursement voucher and included in the cost. 2. The receipt can only prove the cash relationship and cannot be included in the cost.

Legal basis: Measures for the Administration of Invoices in People's Republic of China (PRC).

Article 3 The term "invoice" as mentioned in these Measures refers to receipts and payments issued and collected in business activities such as buying and selling commodities, providing or receiving services.

Article 20 All units and individuals engaged in production and business activities shall ask the payee for invoices when they pay for goods, services and other business activities. When obtaining the invoice, you are not allowed to change the name and amount.

Twenty-fifth, except for special circumstances stipulated by the competent tax authorities in the State Council, invoices are only used by purchasing units and individuals in this province, autonomous region and municipality directly under the central government. The tax authorities of provinces, autonomous regions and municipalities directly under the Central Government may stipulate the methods for issuing invoices across cities and counties.