is what I'd call it, given that taxes are not the same from one country to another, and to keep it close to the French. A number of translations of French and Swiss sites call it that, and some Indian sites refer to their own "professional tax" too. Even the State of Tennessee has one:

TWO HUNDRED DOLLAR ($200) PROFESSIONAL TAX
In accordance with Tennessee Code Annotated, Title 67, Chapter 4, a two hundred dollar ($200) tax is imposed on the privilege of engaging in the following vocations, professions, business or occupations:
LOBBYISTS, BROKER-DEALERS, AGENTS, INVESTMENTS ADVISORS, ACCOUNTANTS, ENGINEERS, ARCHITECTS, LANDSCAPE ARCHITECTS, REAL ESTATE PRINCIPAL BROKERS, CHIROPRACTORS, DENTISTS, PHYSICIANS, PHARMACISTS, PSYCHOLOGISTS, OPTOMETRISTS, VETERINARIANS, AUDIOLOGISTS, OSTEOPATHIC PHYSICIANS, PODIATRISTS, SPEECH PATHOLOGISTS, AND ATTORNEYS.
This tax is due and payable on June 1 of each year with the first payment due on or before June 1, 1992. Taxes paid after June 1 are delinquent. Penalties and interest shall be assessed in accordance with the provision of Tennessee Code Annotated, Title 67, Chapter
(Also referred to as "Professional Privilege Tax")

[http://polproc.mc.vanderbilt.edu/policy/att5-10v.html]

Thank goodness Tennessee translators are underprivileged!

I have no particular inclination towards either business or professional; however I DO think it worth pointing out that this is a tax charged by the "commune", i.e. the rate is fixed locally and will vary from place to place. It should not be confused with any national taxes levied, such as corporation tax and suchlike.

Possibly irrelevent for your context, but a point I feel is worth making :-)