QBO: How to send existing invoices to a single customer

On your dashboard, click the "New" button on the top of the sidebar, and select "Request: Send an invoice"

Select "Send invoice(s) to a specific customer"

Here, you can select which contact you want to send an invoice to at the chosen company.

Start typing in the customer name and select the customer and contact that you would like to send invoices to.

Check the invoices that you want paid, as well as the bank account you want all funds to be deposited to, select "Send invoice", and confirm.

That's it! You're good to go.

Prefer to request invoices from multiple customers at once? Look here.