The reason clutter increases complexity is that it obscures the true amount owed by the customer, can confuse the customer, and/or precipitates dispute over the amount owed.
In contrast, the collection of a whole, open invoice begins as a simple COLLECTION CONTACT. An underlying dispute may be identified, but often the contact revolves around when the invoice will be paid, not if and how much. However, dealing with clutter requires significant time and discussion trying to establish the amount owed, not when it will be paid. Often it triggers additional research and provision of documentation before the topic of when payment will be made is even broached. Clutter increases the difficulty of collection.

Заранее благодарю