There are a couple of reasons why QuickBooks Online (QBO) auto-generates duplicate and triplicate copies of your invoices when creating them. These are the following:
The Automatically invoice unbilled activity feature is turned on.
Auto-synced transactions from a third-party app.
Full browser cache which causes unexpected QBO behavior.
First, let's ensure to turn off the Automatically invoice unbilled activity on the Account and Settings page. This way, QBO won't auto-generate invoices for unbilled activities moving forward.
Click the Gear icon at the top, and then select Account and Settings.
Choose Advanced, and then click the Edit ✎ icon in the Automation section.
Select the Automatically invoice unbilled activity radio button to turn it off.
After adjusting your settings, click Save, and then Done.
You can go to the Sales page or use the Audit Log to view all auto-created invoices in QBO.
Second, if you're using a third-party application to download your invoices, it can cause duplicate entries in QBO. Thus, I recommend contacting their support team. This way, they can help you find ways on how to stop the said scenario from happening. Otherwise, you can manually delete your invoices in QBO.
If this isn't the case, then the browser's piled-up cache can be causing the issue. I have a different set of steps to help fix this.
To start, please access your account using a private window or an incognito. This helps ensure your browser doesn't store any data in the cache. You can use the following shortcut keys to access one:
Ctrl+ Shift + N for Google Chrome .
Ctrl + Shift + P for Mozilla Firefox and Microsoft Edge .
Command + Shift + N for Safari .
Once there, try creating a sample invoice again. If it works this time, please go back to your regular browser and clear its cache. This helps to restore the default setup of the browser and refresh the system.
To keep track of your invoices in QBO, you can pull up invoice-related reports in QBO. To do this, go to the Reports menu, and then select the desired report from the Manage accounts receivable section.
Just tag my name in the comment section if you have additional questions regarding this. I'd be happy to help you some more. Take care.