A belated birthday is a birthday greeting that is sent after the actual birthday has passed. It is a way of apologizing for being late and still wishing the person a happy birthday. The phrase "belated happy birthday" is the correct formulation, as "belated" means something that is late or delayed, and "happy birthday" is the greeting. The phrase "happy belated birthday" is not exactly logical, but it is still commonly used in the United States. It is important to note that the birthday itself cannot be "belated" as it is a fixed event, so the phrase "belated happy birthday wishes" may be preferred instead. When you miss someones birthday, sending them belated birthday wishes as quickly as possible should be your priority, and it is recommended to send a text message or an email in addition to a card.