Thank you for the reply, but you solution did not work. My apologies if my original post was not clear. I am not looking for CUSTOM transaction numbers. I'm looking for the SYSTEM GENERATED transaction numbers that QBO automatically assigns to each transaction. Again, this is available in QuickBooks Desktop. I'm looking for the same in QBO.

I've attached an screenshot image of the customization options available under the "Transaction Detail by Account" report in QBO. You'll see that transaction number is not available.  BTW... neither the custom or system transaction number is available (I tried turning custom numbers on as you suggested, and even that doesn't show).