@Rustler, I was going to suggest journaling the relevant amount out from A/P to the LT liability account, and then "paying" the bill with that transaction thereby marking it as paid. Arithmetically I think that achieves the same effect as your method, but yours seems cleaner[1]

Would you also use your method where the bill did not have inventory items -- a purchased service for example? Obviously your comment about driving the inventory asset account negative then would not apply, but I don't see why that would matter. I definitely don't like the deletion approach that @Steve_C  suggested!

Thomas

[1] Not least because it avoids using the journal which QB Online (unlike ye olde QB Desktop) seems very confused about, in terms of how to display journal entries within a Supplier's transaction list.