Paythen has some direct integrations β a native WordPress plugin that lets you offer Paythen in minutes on your WooCommerce store (more), a companion product called Cardivo (built by us) that lets you offer digital gift cards that are redeemable on your Paythen plan pages, WooCommerce store or even manually for other scenarios (more).
For Shopify, because of API access limitations imposed by Shopify, there is an email-based workflow that sends customers an eamil with their payment plan link once they check out. Read more on that here.
For all other integrations and workflows, we have our fully featured and constantly improving Zapier app that lets you send data from Paythen into other systems, or lets you send custom payment plan links via email based on actions in your other systems. Using our Zapier app, you can send data to and trigger payment plans from over 7,000+ other tools so most workflows you can envision are available.
At the moment, Paythen does not have an open, publicly accessible API. If this is something you’re interested in, let us know via the chat icon as that helps as prioritize future features better.