The ability to import an IIF file is exclusive to QuickBooks Desktop. If you wish to import your files to QuickBooks Online (QBO), you can do so via a CSV file.
Say, you want to import your products and services. Follow these steps:
From the Gear icon, select Import Data.
Note: The next page will show you a list of everything you can import in QBO, which are Bank data, Customers, Vendors, Chart of Accounts, and Products and Services.
Tap on the Products and Services button.
Hit the Browse button to look for the file you want to upload.
Note: You can click on the Download a sample file link to see the correct format of a file you can upload.
Search for your file. Select Open, then Next.
Map your fields, then select Next.
Tick the Overwrite all values for each product or service with the same name.
So what this tells me is that any company with any kind of history cannot make the change to Quickbooks Online if they have any kind of desire to retain their accounting history since QBO does not support the import of transaction import...even as csv file format.
Sounds like we need to find an alternative accounting system as this will not work.