As a workaround you can attempt the following:

1. Enter a credit invoice to reverse or offset the invoice you are attempting to change.
2. Record a 0.00 payment to pay the original invoice and the credit invoice together.
3. Enter a new invoice to replace the original invoice but includes the changes you were attempting to make.

If this does not work, contact Sage Customer Support to examine your data and determine if a file fix is needed or if another workaround is available for your situation.

Change Invoices hangs when attempting to change an invoice in Accounts Payable