Thanks for joining the thread, Base 12 Design.

The steps you've shared is correct when importing Customer, Vendor, Items, and Chart of Accounts from an Excel spreadsheet in QuickBooks Desktop. However, you'll need a 3rd party application to import invoices.

To do this, you can follow the instruction provided by Fiat or look a third party software that has the capabilities using this link: QuickBooks Apps.

You can learn more about QBDT's export and import capabilities by visiting this link: Export, import, and edit IIF files.

When you've discovered the app that suits your needs, you can read this page for references in case you need to reconcile your accounts later: Reconcile an account in QuickBooks Desktop.

If you need anything else in QuickBooks, let us know. We're available to help at any time.