Hi there, @DanBu.
Allow me to share some information about your concern a customer report that will show average days "past due" (NOT average days to pay) in QuickBooks Desktop (QBDT).
The Average Days to Pay Report displays the data of the current total average time your customers pay you. However, the term Net 30 where a customer pays on Day 40 and the payment is 10 days past due is not yet available in QBDT.
Furthermore, the option to eliminate the data for the terms Net 60 where the customer pays on Day 40 and was paid early and not within the past due time of the payment is also unavailable. Nevertheless, as a workaround, you can export the data to Excel and customize it outside QuickBooks.
Additionally, here are some articles that you can read to help speed up the review process and personalize your reports in QBDT:
If there's anything else you need to accomplish for your customer report, please let me know by leaving a comment below. I'd be more than happy to work with you. Keep Safe!