Hello Erik,
Method has the ability to send emails to multiple people in the same company. When a contact for a company unchecks "Opt Out Of Billing?" in the Edit Contact screen, they will get invoices sent to the company from Method. This way multiple people from the same company can receive the same invoice. In QuickBooks, the invoice is sent to the company's email address and not the contact(s) email. I'm not an expert in QuickBooks, but I did some tests. If you need to send the invoice to multiple people in QuickBooks, you would have to have multiple email addresses in the main contact for Method. You can do this with using a semi-colon, ';', to separate the emails. Such as mary@anywhere.com;todd@anywhere.com. In Method, you send the invoices out once it is made.
We also have the List Builder under the Campaigns tab to send out invoice reminders to a batch of customers. Check it out. You can select to add invoices from a selected date and balance to add to your list. In Step 4, you can choose your email reminder that goes to customers reminding them they have an invoice due.
Greg