Hi, there @AndrewR1.
I know this is new to your end but let me give you insights on why your invoice number suddenly changed from 2000's to 183,000+.
Since QuickBooks Online depends on the data that were input by the user, a possible reason that it was messed up, perhaps the user accidentally entered the wrong numbering sequence of an invoice. You can check them in your audit log.
Here's how:
- Go to Settings and select Audit log.
- Select Filter.
- Use the fields on the Filter panel to choose the appropriate User, Date, or Events filter to narrow the results.
- Select Apply.
To fix the sequence, create a dummy invoice with the correct invoice number sequence, so that QuickBooks Online will follow the next invoice digit number according to the last sequence that was input, after that, you can now delete the dummy.
For a more detailed point of view, you can refer to this picture:

Moreover, I'll be sharing the following resources to help personalize and manage your invoices in QuickBooks Online:
- Customize invoices, estimates, and sales receipts in QuickBooks Online
- Record invoice payments in QuickBooks Online
Let me know if you have any other concerns or questions about your invoices. I’m here to help. Keep safe!
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