# 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.

## Data Retention

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.

## 95th Percentile Calculation

For 95th Percentile billing, the default behavior is to use the
highest of the input or output 95th Percentile calculation.

To instead use the combined total of inout + output to derive the 95th percentile,
This can be changed on a per bill basis by setting 95th Calculation to "Aggregate".

To change the default option to Aggregate,
add the following the `config.php`:

```php
$config['billing']['95th_default_agg'] = 1;  // Set aggregate 95th as default
```

This configuration setting is cosmetic and only changes the default
selected option when adding a new bill.
