How to add Plan/Addon/Coupon specific contents in the Invoice Receipt email?

To add Plan/Add-on/Coupon specific contents to the Invoice Receipt email notification, navigate to Settings > Configure Chargebee > Email notifications > Invoice Receipts and click on the "Edit" option.

You can select the subscription details that you would like to show from the pop-up. Refer to the screenshot attached below.

To add specific content based on the plan type you can set up the Segmentation feature that allows you to send different email content to different sets of customers filtered based on the plan they're on. Here's more on segmentation.

To send specific content based on the addon/coupon type, you can use Mail Merge tags. Here's the format.

Coupon Specific

#line_items

#line_item.type= coupon_credit

#line_item.description=summer // summer is a one time coupon

Summer is a one time coupon and it'll not be applied on your next invoice

/line_item.description=summer

/line_item.type= coupon_credit

/line_items

All the available Mail Merge fields are available on the edit template page as in the screenshot below: