I believe our support agent has replied to this question via ticket ID: 73634
Here's the reply from the ticket:
When using the checkout existing subscription API, the promotional credits if present for the customer would automatically be displayed on the checkout page.
Screenshot attached for your reference.
The checkout new subscription API call will not contain any promotional credits as it cannot be used for an existing customer. The reasoning behind this is that the existing customer will already have a credit card on file, hence he need not perform a checkout operation again.
However, if the customer is on a trial period, then he can perform a checkout using the checkout existing subscription API.
Here is the checkout page we generated for your test site with promotional credits on order summary:
I hope this helped. Let us know if you need any clarification.
yes, thank you for your reply, i wanted to open a ticket, instead i made a question in the forum. Sorry for that.
No worries, Mauro. :)
Hope we were able to answer your question. Please feel free to reach out to us (email or forum posts) for further assistance.