Hi there,
I'm excited to hear you're making the switch to QuickBooks Online. Your customer list and invoice list may include tons of data, so it's essential that you're able to easily import this into QBO. I'd be happy to explain how you can do this.
You're able to import your customer list and invoice list by clicking the Gear icon > Import data. These files will have to be Excel or CSV files. Once uploaded, you'll review the mapping and then you're all set!
If you're not sure how to generate an Excel or CSV file from your current accounting software, you'll have to reach out to their team in order to get things resolved.
I hope this helps! If you have any other questions, please reach out to our tech support team.
Cheers.