Because it is necessary to verify the taxpayer's billing information. Taxpayers use personal income tax APP to scan the QR code generated by the merchant's electronic invoice service platform, and then complete the invoicing after confirming the invoice header information. For the payee, scanning the QR code for invoicing can effectively reduce the input errors of invoicing information, shorten the waiting time for invoicing, standardize the way to obtain invoices, and facilitate reimbursement. Therefore, the tax app should scan the QR code to verify the taxpayer's billing information.