Dear business owners: tread carefully the next time you feel like thanking your customers. Because believe it or not, Citigroup owns that.

Citigroup managed to wrangle themselves a trademark on “THANKYOU” (along with some catchy variations), and now they’re suing AT&T for saying “thanks” to their customers. The claim states that Citigroup is concerned about “customer confusion,” and they don’t think it’s fair that AT&T might actually be making money by saying thanks. Because only Citigroup is supposed to be able to make money that way.

The legal plot thickens further as the source of the complaint is revealed: a rewards program launched by AT&T called “AT&T Thanks” that connects its cell service with a credit card backed by—you guessed it—Citigroup. You’d think that AT&T would have stayed away from that verbiage knowing they would be using Citigroup’s credit services—Citigroup does, after all, use “thank you” all over the place in their marketing, even going so far as to own the domain But apparently the wireless technology right hand didn’t talk to the financial services left hand, and a whole lot of lawyers are now reaping a windfall.

It’s a weird story, but one you might want to keep in mind when creating trademarks for your own business.

Wait, can I trademark a common phrase too?

Isn’t the very purpose of a trademark to provide a distinct mark that clearly, specifically identifies one unique business or service? Why would someone trademark a phrase like “THANKYOU” in the first place? Everybody says “thank you,” right?

True. But everybody also says “Apple.” So if you think your business might really want to trademark some phrase or word everyone has already heard—like “Let’s roll,” for instance—you might actually be able to do it. The key thing to keep in mind when it comes to registering common words and phrases is that context is everything. In other words, it all depends on what you’re selling. If you’re selling lemons, for instance, don’t even try to get a trademark for “Lemon” (though it might work for a used car dealership).

There’s good advice out there on how to avoid trademark infringement, or how to go about getting a trademark in the first place. One place to start educating yourself on the basics is the United States Patent and Trademark Office. There you will find a video offering instruction on how trademarks affect the process of selling products and services, as well as a walkthrough on the difference between trademarks, patents, copyrights, domain names, and business name registrations.

Trademark and similarity

Of course, there are many important factors beyond trademark infringement to think about when you’re trying to pick an appealing name. But when you’re thinking specifically about the possibility of trademark infringement, you need to keep two kinds of similarity in mind.

The first is similarity of the business or service. Two (or more) companies can use the same trademark, provided they are not in similar industries. Thus both a computer maker and record company can (and do) have the same tradename: Apple. The second is similarity of the word or phrase. If you want to name your fledgling retail store “Apple’s Emporium,” you better not sell computers. Or records. Otherwise you’re asking for trouble—even if your last name is Apple.

If you’re close to the line on either of those types of similarities, consider stepping back and reassessing how you’re thinking about your brand, and how attached you want to be to a certain word or a clever turn of phrase. Maybe spending a little more time in the brainstorm/creative phase will yield a better—and less potentially litigious—option.

Be prepared for a fight

Still, you can beat your head against the wall for only so long, and the sad truth is that no matter how much due diligence you do, or how hard you try to be original, there’s always some likelihood of confusion when it comes to trademarks. Crazy as Citigroup’s lawsuit sounds, when it comes to trademarks, suits of this nature occur with alarming frequency.

All kinds of alleged trademark infringements get people sued. Things can get downright strange, in fact. Take Strange Brewing v. Strange Brew. Or Strange Music v. Strange Music.

Is Citigroup going to win their lawsuit? Like everything in the heavily nuanced world of trademark law, the answer is, “it depends.” Essentially, the key question is this: Can they convince the court that AT&T is really confusing its customers or weakening the impact of their “THANKYOU” trademark? As in, “Hey, honey, this email says ‘thank you.’ Is it my bank statement or cellphone bill?”

But whatever the outcome, the case serves as a reminder to put some thought—and research—into your choice of trademarks. And if you think there’s any possibility that your clever name or slogan might infringe on someone else’s, consult an intellectual property attorney.