> ## Documentation Index
> Fetch the complete documentation index at: https://billing-help.nace.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# How to use this documentation

> How to find what you need in the Billing docs

## How this site is organized

* **NAPA & Billing** — How NAPA works, the invoice flow, types of invoices (client vs provider), and how disputes are handled.
* **Billing app** — The application you use every day: what it does, how to upload documents, review and approve invoices, and which environment to use (test, demo, or production).
* **Help** — Who to contact for access, login issues, or other questions.

## Finding what you need

* New to NAPA? Start with [Billing overview](/billing/overview) and [How to use NAPA](/billing/napa).
* Need to do something in the app? Go to [Using the Billing app](/frontend/using-the-app).
* Not sure which URL to use? See [Environments](/frontend/environments).
* Need help? See [Contacts and support](/help/contacts).