Thank you for following my peer's recommendation, Lesley. Another important aspect to check is whether the Bcc and Cc fields contain the same email.

This could be why duplicates are sent when you issue an invoice reminder. Let me guide you on how to check this via a web browser:

1. Navigate to the Invoices section and select the Invoices tab.
2. From the Status drop-down, choose Unpaid.
3. Locate the recently double-sent invoice and click View/Edit in the Action column.
4. Click on Email. You'll see that each Cc and Bcc field indicates 1 (representing 1 associated email); please click on it.
   
   
   (view in My Videos)
   
   

To prevent this from recurring, make sure the email addresses you use in the Cc (carbon copy) and Bcc (blind carbon copy) fields are filled in correctly.

If neither the Cc nor Bcc fields contain any emails, please contact our QBSE Live Support for further assistance. Rest assured, our team has the appropriate tools to access your account and resolve any issues securely. Here's how:

1. Click on (?) Help on the upper right.
2. Select Contact Us.
3. Detail your concern regarding the double-sent invoice and hit Continue.
4. Choose either Chat or Callback for communication.

Our chat and call support is available Monday to Friday, from 6 am to 6 pm.

After this, you could connect your bank account in QuickBooks Self-Employed to accurately categorize customer payments and other transactions into the appropriate self-employed categories.

Please let us know in the comments below if you need further assistance with emailing invoices or if you have other QuickBooks-related concerns.