Hi there, chonkyfire3000.

In QuickBooks Online, the system will automatically set the invoice number when the Custom Transaction Numbers option is turned off in the settings.

Seeing that you still have duplicate invoice numbers, we recommend contacting our Customer Care Team again. We will investigate the issue with our engineers.

Here’s how you can reach out to us:

1. Click the Help icon located in the upper right-hand corner.
2. In the Help window, click the Contact Us button located at the bottom.
3. Enter your question and click Let's talk.
4. Select Start messaging or Get a callback.

For other questions or concerns, please don't hesitate to reach out to us here. Thanks.