In order to amend an invoice using Corrections you must first ensure that the invoice is in the Current Year and sometimes the current period depending on the change you wish to make:
In Dimensions, click the Debtors or Creditors tab. Depending on where your invoice is sitting.
Click Suppliers or Debtors
Find the Supplier or Debtor that the invoice is sitting in
At the top, click Transactions
Click List Definition (5th icon in the ribbon)
Use one of the Field Names to find your invoice based on specific details for that invoice.
Select and right-click the invoice and select Correct
Click Edit
Correct and amend the details for the invoice. Note: The Account cannot be changed if not in the Current Period.