International consulting firms offering a wide range of services (tax, audit, advisory...) are the first port of call for multinational and foreign companies intending to set up business in Luxembourg. They are in a good position to advise their clients on complex legal and fiscal issues, as well as guide them through the process of establishing a new operational entity, recruiting personnel and relocating current employees not living in Luxembourg.

The "Big Four" are Deloitte, Ernst & Young, KPMG and PricewaterhouseCoopers (PwC). They all have been present on the Luxembourg business stage for many years where they compete with both, other well-known companies, such as Tata Consultancy Services, McKinsey and Mazars, and local firms covering specialist niches. International consulting networks are also well represented, such as Taxand, a global network of tax advisors, whose Luxembourg partner ATOZ had been elected 'Best Tax Adviser' at the Finance Management Awards 2009. Whatever the nature of their advice – be it strategic consulting, management consulting, auditing or even IT and HR - each company relies on a pool of experts to meet the needs of their clients.

These firms, like the "Big Four", are also essential animators of the Luxembourg business landscape. Their input ranges from organizing events such as seminars on Luxembourg eBusiness and specialized economic conferences (like the Journées de l’économie) to stimulating the local economy and sharing new management concepts and organizational methodologies. All of these events help professionalize local companies. Some international consultancy firms took this idea even further and decided to establish a center of excellence in Luxembourg. One such example is Tata Consultancy Services with an expert team for its private banking department.

Relying on their capacity to analyze markets and professional practices, the consulting companies regularly compile studies of overall trends affecting various sectors of the economy.

Moreover, these companies play a vital role in developing new sectors as they are involved in the facilitation, promotion and organization of international cooperation. For example, PwC Luxembourg paved the way for a scientific partnership between the U.S. and Luxembourg which led to the establishment of a biobank in the Grand Duchy.

Entrepreneurs like to invest in Luxembourg because major service consultancy firms offer them help as they set up their companies. To this end, McKinsey has developed a methodology for a support network called 1, 2, 3, Go with the purpose of transforming great ideas into sound business plans.