This is not available for businesses based in the USA[1]. Also, the maximum amount for a single transaction is €5,000, which is inadequate for many (most?) B2B SaaS products.
[1] https://gocardless.com/faq/merchants/international-payments/
[2] https://gocardless.com/faq/merchants/
edit: link #2
https://gocardless.com/