

I would go for Consulting. "Consult" looks and sounds incomplete. "Consultant" and "Consultants" are OK too. We use a "Consultants" domain for other business and have to keep stressing the "s" when we say the name. Fortunately we also own the same name in the singular "Consultant" version, which forwards to the plural domain in case someone forgets the "s". "Consultancy" is a less common version and would likely be misunderstood or misspelled.
consult because it is short and simple
In this case, just because "consult" is the shorter word doesn't make it the best one. You wouldn't say "I am a Business Consult", you would say "I am a Business Consultant" or "We are Business Consultants" or "We undertake Business Consulting". I can't see a scenario here where "consult" would work.



