Hello there, Shafferm. 

I appreciate you returning to the thread with further inquiries regarding your vendor loan in your QuickBooks Desktop (QBDT). 

When recording your check with the loan payment and interest, you should enter the check amount as positive since the loan payment is a fee and the interest is a charge of a used asset. 

Furthermore, refer to this article to know more about recording your loan in QBO: Set up a loan in QuickBooks Online. 

In addition, you can check this article for information on how to write off debts if your customer cannot collect them: Write off bad debt in QuickBooks Online.

If you need additional assistance recording your vendor loan, the Community is here to help you. Just let us know by commenting below. Take care, and have a great day ahead!