Hello, @smtwtfs.

Thanks for the prompt response and letting me know the outcome of the steps given by @JenoP. I’m here to help resolve the error on Line 51 so you can import the file successfully.

This error typically happens when the account type selected on Line 51 is different from the one existing in the Chart of Accounts. You can fix this by following the steps below:

First, check the source of the problem.
1.    Save the IIF file to your computer.
2.    Open the saved IIF file in Microsoft Excel.
3.    Look at Line 51 of the Excel spreadsheet. This provides the account name and type that QuickBooks is expecting.

Then, look at your QuickBooks Chart of Accounts to determine the type of account. Once done, make the corrections by doing one of the following:
•    In QuickBooks, update the type of account to match the expected type.
•    In the Export to QuickBooks section, update the account to match the type of account.

That should do it. Give this a try and let me know how it goes. Post again in the Community if you need anything else, I’m more than happy to help. Take care and have a great day!