The simple module allows showing Credit history so they can keep their eye on how the credits are being applied.
The best place to start if you need help with a specific product is to contact the developer. All WHMCS Marketplace developers have both a website and support URL listed.
CleanHTML Invoice and Quote Free template.
As WHMCS does provide tax rules options where you can configure your GST tax but we have some extra features in our module that makes it stand out and necessary to use.
Introduce extra billing models and charge your clients for actual server resource usage.
Send account statements to customers
Allow your clients to automatically login from Invoice Emails