Hi @julie-wormald 

I am coming a bit late to this but you may like to know that there is a data import utility called Zed Axis that can import IIF files into QuickBooks Online you can find it in the Intuit Marketplace.

That would mean you dont have to mess around with trying to convert IIF files into csv format as Axis can read the IIF file translate it and then import it directly.

Hope that gives you another option.