How to change the invoice tax rate from 1 to 1. Log in to Ukey version of VAT invoice software, enter the system setting page, and select the custom goods and services code. 2. Select the item with tax rate of 1, and click the assign code on the right. 3. Select the tax code corresponding to the selected project, select tax exemption in the tax rate column, and click OK. 4. The 1 tax rate of this project was successfully changed to tax exemption, and the setting was completed.