Does anyone know why on the 1st of the month invoices are duplicated with new invoice numbers by quickbooks and then emailed to the customer automatically?

I got an idea on why invoices are duplicated in QuickBooks Online, watertek-plumber.

There's a great chance that you have Scheduled recurring template for the invoices. Hence, the invoices are duplicated every 1st of the month. Here's how to review the recurring templates:

1. Click the Gear icon in the upper-right corner and select Recurring transactions.
2. Look for the recurring template that is set to Scheduled in the TYPE column.
3. The recurring dates will also appear in the INTERVAL column.
4. Click Edit to change the type from Scheduled to Unscheduled or Reminder.
5. If you want to delete the recurring template, you can click the drop-down arrow-next to Edit.
6. Select Delete and Yes to confirm the action.

You can use this link for reference: Edit a recurring template.

If there is no recurring template that matches the invoices that were previously created, I'd recommend providing more details about it. This would help us review other factors that might be causing the duplicates. Thanks in advance and have a great day!