This is a question asked by an Awakened Healer who moved from Kartra to Coach Builder Pro. A client had made her first installment payment in Kartra.
For this unique one time situation it's probably easiest just to send out a recurring invoice (mentioned in the video).
But before doing this, if you haven't already checked (and if you had Stripe connected to Kartra), I would recommend logging into your Stripe account to make sure their isn't an active subscription or payment plan still in progress for that client to avoid the error of charging her twice.