The IIF File Extension, Intuit Interchange Format is a proprietary text file used by Intuit's Quickbooks software for importing and exporting lists and transactions. As of 2004, QuickBooks can also import data using the XML-based qbXML file exchange format.
This file format belongs to Document File category.
IIF File Extension is support by Intuit Quickbooks
Intuit introduced Quickbooks and Intuit Interchange Format or IIF File Extension also known as Quickbooks Interchange Format, IIF is a proprietary text file used by Intuit's Quickbooks software for importing and exporting lists and transactions.
application/qbooks, application/qbookspro, text/iif
Unspecified
Default location of IIF is:
C:\Program Files (x86)\Intuit\QuickBooks 2017
but If you're using different version of Quickbooks, last folder name may vary like Quickbooks 2017 or 2016 or 2015 so on. Last folder name follow this naming convention: "Quickbook followed by the version name"