...
To do so, open the Billing Settings( Billing→Advanced→ Settings), then choose choose Credit Note Number Prefix from the Money Invoices section:
Here you can include a unique alphanumeric prefix before the sequential number.
...
Similarly, to set the Debit Note Number Prefix, select the option from the Money Settings Invoices Settings section, and set the desired prefix.
The system will then allow you to easily select the desired credit note prefix type when creating a credit note.
...