Can I use former client names in advertising?

It is safest to obtain permission in advance from any officer of the client. Seeing your name used without prior permission will make a lousy impression. Issues like implied endorsement and other matters may arise, especially if the client's name is also their trademark.

You do not mention the nature of your business or the advertising media. At a minimum, you should get permission from the client and/or individual who provides a testimonial. You should also get approval of the advertising, itself. There could be other requirements or restrictions, as well, depending on the nature of your business, the medium, and the client.

Unless you owe this client some other duty like as a fiduciary or are bound to an NDA/NNN, etc. merely stating that you served them and using their text name descriptively in your copy should not expose you legally, but this does not make that good policy. As noted, many entities respond negatively when their name is used without permission and if you cross the line and present as if you have their endorsement it may be grounds for trademark infringement. Further, once you make that public then any other potential customers would now know who to call for a reference, so if they are ticked off about the fact that you used their name without asking don't expect a good one. Also and as noted, some industries are governed by a code a ethics that might further restrict you from doing this without express permission like law or medicine. What you should so is have a master service agreement drafted that will not only protect all your interests but can also cover this release as well. This way you get that permission in writing and of course you should always be prepared to remove any reference if they protest so if you are planning on investing in a broader and expensive campaign that includes using their name make sure you check again that they are ok with that. I suggest that you consult with a lawyer in private and discuss your objectives in more detail. You can start by calling around to several for a free phone consultation, get some insights then pick the best fit to work with. Best regards, Frank Natoli-Lapin, LLC