Can we edit tax rate/amounts for AR Invoices once saved

Summary

Can we edit tax rate/amounts for AR Invoices once saved

Content

Hi,

We are driving tax rate on AR invoice based on memo lines entered by the user. As soon as the user saves the invoice, the tax is calculated based on tax engine. However, there are certain exceptional cases, where user would like to override the tax rate and amount calculated by the system after the invoice is saved but before completing the invoice. I have checked this scenario and it seems once system calculates the tax after invoice is saved, it doesnt allows you to update the tax line. Has anyone faced this issue before? Can someone please confirm if