WHMCS is a leading billing and support automation system used by thousands of web hosting companies. It is used to manage web hosting billing for their clients and offers auto provisioning services. This helps to web host to setup clients’ accounts automatically and other automated tasks (i.e. invoice, notifications etc.).
Users can directly raise a support ticket from their billing area. WHMCS also allows to integrate third party helpdesk like Kayako and allows the users to manage billing and support using single login.
In this article we will describe you how to upgrade WHMCS version. WHMCS provides two types of distribution as follow:
A full release contains all the files of WHMCS installation. It can be used to perform new installation or upgrade WHMCS on an existing installation (regardless of previous version).
A patch set contains only the files that have changed from the previous version. A patch set can only be used if you are using the previous version than the current release i.e. a patch set of version 1.1.1 is only valid those users who are using WHMCS version 1.1.0.
How to upgrade WHMCS using full release
Before you start upgrading process, it is strongly recommended that you secure the full backup of your installation (i.e. your WHMCS database and all files). Please note that since this is a full version, any changes you have made in the default templates will be wiped and you will need to make those changes again. Once you take full backup, you can proceed to next step.
 First obtain the latest release from your WHMCS client area. Make sure that you are downloading full release.
 Unzip the downloaded file on your local computer. If you have rename your “admin” folder, make sure you rename it in the unziped folder. Similarly if you have customized “crons” folder, be sure to upload it to the custom location.
 Upload your WHMCS installation files to your existing installation and replace any existing files and folders.
 Once all files are uploaded successfully, visit your WHMCS URL which should redirect you automatically to upgrade process. If you get a message saying WHMCS is not installed, this indicates you have overwritten the configuration.php file for your installation. Do not proceed from here. First you will need to restore your configuration.php file from backup.
 Accept WHMCS End User License Agreement and follow the steps on screen to upgrade your database.
 When prompted, delete the install folder from your server.
How to upgrade WHMCS using patch set
Before you start upgrading process, it is strongly recommended that you secure the full backup of your installation (i.e. your WHMCS database and all files). Once you take full backup, you can proceed to next step.
 Download the patch set using the link provided in the release announcement.
 Unzip the patch set files on your local computer. If the patch set has “admin” directory and if you are using different folder name, make sure you rename it.
 Upload all the files to the root directory of your WHMCS installation replacing any existing files and folders.
 Visit the admin area of your WHMCS installation to trigger the version number bump and complete the process.