A past due invoice is a billing statement that hasn’t been paid by a client by the invoice payment due date. Past due invoices are commonly known as overdue invoices. It’s important that small businesses track past due invoices to preserve cash flow. Overdue invoices record outstanding debts for effective accounts receivable management. Thousands of small businesses use simple invoicing software like Bookipi to track overdue invoices. Businesses can easily follow up invoice payments by automating sending overdue reminders or imposing late fees.