Complain directly to the tax authorities. China's Law on the Protection of Consumers' Rights and Interests and the Measures for the Administration of Invoices in People's Republic of China (PRC) clearly stipulate that when consumers ask for purchase vouchers such as invoices, operators must show them. If a merchant refuses to issue an invoice or shirks it by means of IOUs, he can directly complain to the tax authorities, and the tax authorities will punish the merchant who refuses to issue an invoice according to the investigation results.