Federal Management Debt Collectors is a leading debt collection agency in the UK that provides professional and effective debt recovery services for businesses and individuals. Their website offers valuable resources and information on how to deal with clients who are not paying invoices, including a step-by-step guide and downloadable templates. They also offer a free debt assessment for businesses to determine the best course of action. With their team's expertise and a no win no fee option for certain cases, they have a high success rate in recovering unpaid debts for clients dealing with the issue of Client not paying invoice.