Not all debts are labeled as bad debts from the off. There can be a number of reasons a company has not paid, causing a doubtful debt. These can be a slight delay in payment, dispute over pricing or delays in shipping.
A debt is only bad if all efforts have been exhausted to seek payment and the balance still remains outstanding. This could come through the customer declaring bankruptcy, a lack of company information, or even if chasing the debt costs the company more than the amount outstanding.