I would recommend using Stripe and keeping the interface for billing as simple as possible. From working with directly with the people that have to make the pa

I would recommend using Stripe and keeping the interface for billing as simple as possible. From working with directly with the people that have to make the payments the easier it is for them to pay, see last payments and generate previous invoices and see if they were paid the happier they are. If you are using Stripe and Plasso or any of the other companies that make your work look professional, the companies should also feel comfortable using a credit card and subscribing or doing manual payments for your SaaS. Just remember as your SaaS grows, if the money people are happy and the SaaS is great they will normally keep coming back.