This is a practice Excel project. I entered and organized sample data and used basic Excel formatting and calculations.

InvoiceKit taught me to describe status work as a transition contract, not a dropdown. For each invoice change, I can name the starting state, permitted action, persisted result, and visible confirmation. That structure also gives deterministic UI checks and live Firebase checks distinct jobs. When scoping a workflow, write one acceptance row per important transition. It exposes missing rules earlier and gives the client a reviewable definition of done.