Prepayment showing available whose BU doesn't exist anymore

Summary:

Content (please ensure you mask any confidential information):

We have an issue where a prepayment was created in the past for UK BU, it was paid with multiple payments, but it was never applied to any invoice.
Now the UK BU is closed, and we can't create any invoice for the supplier because the supplier is also not there in the system.

User wants this prepayment to be get off the list of available. Please suggest how we can achieve this.

Version (include the version you are using, if applicable):

24B (11.13.24.04.0)

Code Snippet (add any code snippets that support your topic, if applicable):