1. Open the billing software and set "Use User-defined Classification Coding Mode" in System Parameter Settings-Parameter Settings-Operation Parameters. 2. Open the original commodity code: system settings-commodity code-VAT commodity code (motor vehicle product code and cargo transportation commodity code are selected respectively for motor vehicle or cargo transportation) 3. Add categories first: click the commodity information category-"+"-enter the category name, such as 04, add commodities and assign codes: click the Add button-enter the commodity name, such as catering expenses-click the assignment code (or click the assignment code 5). You can find the relative category by keywords-click Select-select tax rate-check whether tax is included-click OK 6. Click OK after the prompt operation is successful; You can use it when invoicing. 7. Invoice issuance: invoice management-invoice filling-invoice type selection (such as ordinary invoice) 8. After entering the buyer's information, select a commodity to be delivered. You can select ""to select the commodity. 9. Select our coded product and double-click it. 10. After filling in other information, click Print to successfully issue it.