According to Hallmark, birthday wishes to a co-worker depend on one's relationship to the person celebrating a birthday. For a friend's birthday, special wishes can be a bit casual, but for a supervisor, birthday wishes are more formal. One example of a birthday wish is: “Happy Birthday and all the best to you in the year to come!” Short notes can include "celebrating you" or "Hope it’s a happy day!”
Hallmark reminds co-workers to avoid talking about work-related assignments or topics in a birthday card. Instead, when signing a card, the signer simply adds good wishes related to that person's special day. A more formal birthday card can say "best wishes and good luck on your birthday." However, if the co-worker in question is more like a friend, a good-spirited joke or more personal sentiments are acceptable.
Hallmark gives an example of a birthday message that is on a lighter note, with a statement about all work and no play leading to dull lives and encouragement not to work too hard on her birthday. If the signer is one of the last people to sign a birthday card, she can find it difficult to write a unique message as all the obvious ones have been taken. An appropriate saying to include is "honored to celebrate this day with you."