Classifying your per diems is easy in QuickBooks Self-Employed, @ikatsi.

Choosing the correct classifications depends on how you want your transactions to be categorised. In QuickBooks Self-Employed (QBSE), you'll see a list of categories that are modelled after the IRS's Schedule C that you can use. You can check it here for more information: Custom categories in QuickBooks Self-Employed. 

To confirm the correct category your transaction can be classified, I suggest reaching out to your accountant. This is to ensure that all are accurately belong to the correct account and to keep your accounting data from being messed up. If you're not affiliated with one, you may consider using our Find an Accountant tool. 

For your reference about putting your transaction into QBSE, feel free to visit this article: Categorise transactions in QuickBooks Self-Employed.

QBSE also gives you the ability to quickly categorise your transactions by creating rules. Once you make one, you only need to review the categorisation since the program automatically does it for you. 

Drop me a comment below if you have any other questions classifying your per diems. I'll be more than happy to help. Wishing you a good one.