can oner upload historical invoices generated by other invoicing software?

Yes, you can import historical invoices generated by other software into QuickBooks Online (QBO). Since these invoices predate your QBO account, you can import them using a CSV (Comma-Separated Values) spreadsheet.

Here's how:

1. Go to the Gear icon.
2. Under the Tools section, click on Import data.
3. Select Invoice.
4. Click Preview what's required to be guided on what you need to fill in.
5. Upload your CSV file and check the boxes if needed.
6. Then, click Next.

Please respond to this thread if you have additional concerns. We’re here to help.

​@Robert Mulder Another option, you can purchase a 3rd party service to migrate your invoice data.