If you wish to give customers a receipt/payment confirmation whenever they pay an amount off their booking, a "Payment Confirmation Email" template can be set up.
Open the relevant Product in Intellibook
Under the "Content" tab, open the "Payment Confirmation Email" tab.
Click "Edit" to start creating/changing the template:
Apply the message you'd like to use for this email as shown in the below example:
See the Product content templates article (including the "Payment Confirmation" section contained within) for more information about personalising the content of this email using placeholders.