Many happy returns is a phrase often used to wish someone a happy birthday. However, there are many synonyms that can be used to convey the same sentiment. These include phrases such as "wishing you a wonderful birthday," "happy birthday with all my heart," "may your birthday be filled with joy," "sending you all my love on your special day," and "hoping you have an amazing birthday celebration." Other phrases that could be used to convey birthday wishes include "celebrate your special day with happiness," "enjoy your birthday to the fullest," and "may your birthday be as amazing as you are." Regardless of which phrase is used, the sentiment remains the same - to wish someone a happy and joyous birthday.