If the invoice status is Completed, to add any new changes to it, there are some steps you need to follow:
1. In Finances-> Invoices, open the desired invoice page.
2. Click on Change to Draft button.
3. Add the new changes to the booking.
4. Then come back to the invoice page, and click on Re-generate button.
If you have already Posted the invoice to Xero, to add new changes, you need to follow below steps:
1. In Finances-> Invoices, open the desired invoice page.
2. Click on Void button.
3. Add the new changes to the booking.
4. In the invoice page, click on Re-generate button.
5. Click on Post to Xero button.
