Many third party payroll providers supply a file formatted in an IIF format to be imported into either QuickBooks Pro, Premier or Enterprise. Unfortunately, with QuickBooks Online there is not support for importing IIF files. You can use Transaction Pro Importer on the Intuit App Center
to easily import these files.
You just have to delete a few extraneous rows that are required by Intuit's IIF files. The original IIF files as opened in Excel is below. We will need to delete rows 2, 3 and 12 (these rows are highlighted in yello).
Below is the import file after removing the additional rows of data. Save this file as an excel file pre-import.