User is not able to edit the Tax Rate on an Invoice and assign a rate other than what is set on the Tax Code/Group.
The Tax rate assigned to the Sales order is what the user needs to have on the Invoice, however, such tax rate is already replaced by the current Tax rate as of the time that the Sales Order is being Invoiced.
1. Navigate to Setup > Accounting > Taxes > Set Up Taxes
2. Select the Appropriate Nexus (If Advanced Taxes Feature is Enabled)
3. Disable Per-Line Taxes on Transactions preference
4. Click Save button.
5. Now, edit the Invoice
- Go to Accounting tab, Tax % is now editable.