Okay so either you have a problem with a particular invoice, either it’s:
- A duplicate invoice
- An invoice that will not be paid by the customer (for various reasons) or
- You chose to cancel the invoice (you gave the service or product to the customer instead of them paying it)
As it is good business practice to keep a complete record of all transactions, invoices (and their numbers) should also be retained. Because of this, it’s better to void invoices instead of deleting them.
If you delete the invoice then someone at some point will say “What happened to invoice #1234?”.
If they were able to lookup invoice #1234 and see that it has been voided, preferably with a note to say why it was voided, that’s better than having a completely missing record.
If you’ve already received payment against that invoice, don’t void the invoice. Instead, issue a credit memo or a refund to adjust the transaction.