Is it possible to allocate a new invoice number to an old invoice?

Hello there, @ashdeliveryservi.

Welcome to the QuickBooks family. I can provide some information about the invoices in QuickBooks Online.

Transactions you enter system can be updated for you to add additional details. To answer your question, yes, you can allocate a new invoice number by modifying the sales transaction.

In case you need the steps, here's how:

1. On the left panel, hover your cursor to Sales.
2. Click Invoices.
3. Search for the invoice.
4. Press the drop-down arrow under the Action column.
5. Select View/Edit. 
6. Update the invoice number, then hit Save and close. 
7. If the transaction is linked to others, you'll get a prompt. Click Yes.

Additionally, I recommend the following resources which contain video tutorials to help a user customize an invoice, as well as some steps on how to do it through the QuickBooks mobile app:

• How to edit an invoice [Video]
• Customise invoices, quotes, and sales receipts in QuickBooks Online

Let me know in the comment section below if you have any other questions. Have a great day ahead.