Creating a credit note means that you are creating a negative invoice from that original invoice, which will therefore zero it out in your revenue. Original invoice will stay in your ledger and it will have a credited status. So creating a credit note will not delete the original invoice but it will delete it from receivables.
Credit note will have its own invoice number and it will be shown in accounting reports.
How to create a credit note?
Open the invoice and click on the "Create a credit note" button on the upper right corner:
Confirm that you want to create a credit note by clicking "OK".
Then you can choose if you want to send the credit note to the customer and/ or print it. It is a good practice to send it to the customer but if, for some reason, you don't see in necessary just choose "Cancel".
Please note that partial crediting cannot be done. Instead, the invoice must always be credited in full, and a new corrected invoice must be issued.