There are many positive sayings to write on a retirement cake, such as "Congratulations on your retirement," "We'll miss you, Happy Retirement" or "Have a blast on your retirement!" For a retirement cake, it is best to keep the subject matter happy and congratulatory, and humor can be used, as well.
Some humorous sayings to put on a retirement cake can be "Goodbye tension, hello pension!" or "Retirement: The world's longest coffee break." Any message written on a retirement cake should stay positive and wish good will on the retiree, like a simple "All the best for your future!"