The reason why the sender's signature cannot be verified may be that the digital certificate is damaged, the billing software is faulty or the tax authorities have network problems. Verification refers to the invoice data issued by taxpayers after security authentication and encryption of tax digital certificates. After uploading to the tax authorities, the digital certificate will be verified. The possible reasons for the failure of signature verification are that the digital tax voucher will be invalid and the inspection system of the tax bureau will also lead to the failure of signature verification in the process of uploading online after invoicing and adding digital signature to electronic invoices.