Group 1 - The article discusses the process for travelers to issue electronic invoices (railway electronic tickets) through the railway 12306 mobile app, emphasizing the steps to replace invoices if needed [3][4] - It highlights that electronic invoices cannot be voided once issued, and if there is an error, a red invoice must be issued instead [3] - The article outlines the conditions under which a red electronic invoice can be issued, including scenarios where the buyer has or has not confirmed the purpose of the invoice [4] Group 2 - The article specifies that if the buyer has already used the electronic invoice for VAT declaration, they must adjust their input tax based on the confirmed amount until they receive the red invoice [4] - It mentions that the information regarding the issuance of red invoices is managed by the railway transportation enterprises, which must fill out a confirmation form for the process [4]