Your trial allows a max of 3 email addresses in each field while sending Invoices
Glad to see you in the Community, accounts407.
In QBO, you can only add three custom fields on an invoice (trial or paid subscription). Instead of using these boxes, use the To field and enter the email addresses separated by a comma and space. Please know there is a 100-character limit in the recipients' field and this includes spaces.
Once the subscription expires, make sure to subscribe so you can enter more than three email addresses. Here's how:
Go to the Gear⚙icon and select Account and Settings.
Click the Billing & Subscription menu.
In the QuickBooks Online section, choose Subscribe.
Follow the on-screen instructions to complete the process.
Confirm your payment information and hit Save.
To add the information:
Go to the Sales menu on the left panel to choose All Sales.
From the list, mark the box for the invoice you’re working on.
Navigate to the Action column and choose Send from the ▼ drop-down.
In the To field, key in the email addresses separated by a comma and space.
Then, enter the email addresses in either the Cc or Bcc field.