Split Pay currently supports one active split per customer. The articles below explain why this is the case today and how to think about which bill to split when you've got multiple options. Before your first plan, you can apply for a different bill from your account; starting a new application replaces any approval you already have.
This sub-section also covers the one exception to the rule: landlords receiving payouts can also split one of their own bills, since those operate independently of each other.