Beijing can't get Wal-Mart's invoice. Because it is illegal to buy and sell false or forged invoices, which involves fraud and illegal acts. Invoices from Wal-Mart or other businesses should be authentic and legal shopping vouchers and cannot be obtained by illegal means. You need a formal invoice, which can be obtained through the following legal channels:

1. Ask for it when shopping: When buying goods or services, you can ask for an invoice from the merchant, and the merchant will provide a legal shopping invoice.

2. Electronic invoice: Many businesses now provide electronic invoices. You can provide the corresponding contact information when shopping, and the merchant will send the invoice to your mailbox or mobile phone.

3. Government-approved invoice issuing service: In some countries or regions, government-approved invoice issuing service can help you issue legal invoices.