He's being delinquent on his debts/in paying his debts
delinquent
: failing to pay an amount of money that is owed
: a status that suggests to a lender that you are late in paying your debts. Being delinquent on your debts often means being more than 30 days late twice or 60 days late once. Being delinquent often means your account is handed over to a collection agency for collecting payment. This step not only results in you being called at home for payment, but also undermines your credit history.
: North American In arrears: delinquent accounts
: formal Failing in one’s duty.
... you will learn that once a person in our society has developed a history of being delinquent on his debts he will, most likely, continue those payment habits for the rest of his adult life.
Cash Or Credit?: A Nuts and Bolts Guide to Effective Credit Management