How to view system generated tax details after it has been manually overridden

Hi,

Our current tax setup allows for manual override of system generated tax for payable invoices in case tax rates or tax rules become outdated. As such, we would like the ability to view the system generated tax of an invoice retrospectively: before manual override to allow for comparison.

The question is then, how can we do this in the system?

Any answers would be greatly appreciated.

Thanks,