source: Extensions/Billing-Module.md
# Billing Module

With the billing module you can create a bill, assign a quota to it and add ports to it.  
It then tracks the ports usage and shows you the usage in the bill, including any overage.  
Accounting by both total transferred data and 95th percentile is supported.

To enable and use the billing module you need to perform the following steps:

Edit `config.php` and add (or enable) the following line near the end of the config

```php
$config['enable_billing'] = 1; # Enable Billing
```

Edit `/etc/cron.d/librenms` and add the following:

```bash
*/5 * * * * librenms /opt/librenms/poll-billing.php >> /dev/null 2>&1
01  * * * * librenms /opt/librenms/billing-calculate.php >> /dev/null 2>&1
```

Create billing graphs as required.

## Options

Billing data is stored in the MySQL database, and you may wish to purge the detailed 
stats for old data (per-month totals will always be kept).  To enable this, add the 
following to `config.php`:

```php
$config['billing_data_purge'] = 12;     // Number of months to retain
```

Data for the last complete billing cycle will always be retained - only data older than
this by the configured number of months will be removed.  This task is performed in the
daily cleanup tasks.