> ## 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.

# Using the Billing app

> How to log in, upload documents, and review or approve invoices

## Logging in

* Use the link provided by your manager or IT (test, demo, or production). See [Environments](/frontend/environments) for the difference between them.
* Log in with the credentials or single sign-on (SSO) your organization uses. If you can’t log in, contact the person who manages access or see [Contacts and support](/help/contacts).

## Uploading documents

* When you need to run NAPA **manually** (instead of using the automatic Barton sync), go to the upload area in the app.
* Upload the **contract** and **timesheet** (and **expenses** if applicable), or contract + expenses as allowed by the flow.
* Start the run. The app will show when the job is in progress and when it’s done or needs your review.

## Reviewing and approving invoices

* When an invoice is ready for review, it will appear in your queue or the relevant section (depending on how your team uses the app).
* Open the invoice to see line items and **citations** (where each amount comes from—e.g. contract and section).
* You can **approve** (send to delivery), **reject** (send back for correction), or **edit** where the app allows. Follow your team’s approval rules.

## Handling disputes

* When a client disputes an invoice, open that invoice in the app and use the contract, timesheet, and citations to review the dispute.
* Follow your team’s process for resolving disputes and updating status. For help, see [Disputes](/billing/disputes) and [Contacts and support](/help/contacts).

## If something doesn’t work

* Check that you’re on the right environment (test vs demo vs production). See [Environments](/frontend/environments).
* If you still have issues (e.g. upload fails, wrong data, can’t approve), contact support. See [Contacts and support](/help/contacts).