Sam, the invoice can be issued for six months. According to relevant information, the validity period of special VAT invoice is 180 days. Adjust the deduction period of tax deduction vouchers such as special VAT invoices from 90 days to 180 days. Sam Member Store is a high-end membership store owned by Wal-Mart, a Fortune 500 company. Its name comes from the founder of Wal-Mart, Mr. sam walton, a legendary retail legend.