There are several synonyms for the phrase "owning up to," which means admitting to something or taking responsibility for one's actions. One synonym is "fessing up," which is a more informal term but still conveys the same meaning. "Acknowledging" is another synonym, which implies that one is not only admitting to something but also accepting it or agreeing with it. "Confessing" is a synonym that has a slightly negative connotation, as it often suggests admitting to something wrong or dishonest. "Owning" is another synonym, which emphasizes the idea that one is taking ownership of their actions and their consequences. Lastly, "taking the blame" is a synonym that implies acknowledging fault and accepting consequences for one's actions, even if they were unintentional.