This chapter examines the notion of ‘interdependency’, in two senses: in relation to intimate personal relationships between heterosexual partners, and in relation to the interdependent nature of contributory factors to over-indebtedness. Security is a basic human need. And beyond a necessary level of ontological security, this includes social security – we live in relationships; in a series of social worlds. ‘Close personal relationships’ are defined in this chapter in terms of various forms of couple/family organisation. A survey showed that UK households remained among the most indebted in the world, with British families averaging nearly £8,000 in debts from loans, overdrafts and credit cards. The research explored experiences of using credit and acquiring problematic personal debt in low-income families in the UK, many of whom were reliant on welfare benefits. It draws on two projects, referred to as ‘Credit and Debt’ and ‘Money Advice’. The study used a qualitative longitudinal approach, with repeated telephone and in-depth interviews.