Group 1 - The basic content of invoices includes the title, code, number, purpose, customer name, bank account, item name, unit of measurement, quantity, unit price, total amount, tax rate, tax amount, issuer, date, and issuing unit [4] - The specific content of invoices can be determined by tax authorities based on economic activities and invoice management needs [4][7] - The basic types of paper invoices include the stub copy for record-keeping, the invoice copy as the original voucher, and the bookkeeping copy as the original voucher [6] Group 2 - Tax authorities can adjust the types of invoice copies other than the invoice copy based on the management situation and the business needs of taxpayers [7] - Penalties for losing invoices include fines of up to 10,000 yuan for carrying, mailing, or transporting blank invoices across designated areas, with more severe penalties for serious violations [8] - If invoices are lost or destroyed without authorization, penalties will be applied according to the regulations [9] Group 3 - The announcement from the Ministry of Finance and the State Administration of Taxation specifies that documents such as orders and requisition forms that establish a clear buyer-seller relationship are subject to stamp duty, even if no formal contract is signed [25]