Make unbalanced nodes annoying
Might be a bit controversial and definitely subjective, but if a node is unbalanced, you could add bright red node-flow pair that would make sure it's clear something is undisclosed. Users might hate this, but as a platform that tries to make finances clear and transparent, this could be an interesting idea to explore.
Adminwikibudgets (Founder, wikiBudgets) commented
You are reading my mind :). This will be especially valuable with public budgets, we are testing several UX alternatives.
Jonáš Vacek commented
This could also help users to much better figure out if any data is missing from their budget. Here is an idea of what that could simply look like http://i.imgur.com/sHAhMrd.png