How can I make sure I don't put an invoice in twice, is there a setting to turn on to stop duplicating supplier invoice

Hi coolinahcabins, 

There is a setting within Quickbooks Online that allows you to generate unique invoice numbers whenever you go to create a new invoice.

To turn this setting on, simply follow these steps:

1. Click the Gear icon in the upper-right corner and select Account and Settings.
2. Select the Sales tab and go to the Sales form content section.
3. Mark the Custom transaction numbers box.
4. Click Save and Done.

Once this has been completed, every time you go to create a new invoice it will come up with a different invoice number all the time so you will never get confused ever again!

Hope this helps.

Kristian.