The phrase "this happened later on" can be substituted with a number of synonyms depending on the context. Some alternatives include "subsequently," "afterward," "later," "thereafter," "following that," "at a later time," "in due course," "eventually," "in time," "later down the line," "ultimately," and "in the end." Each of these phrases can add a nuanced touch to the sentence and convey a slightly different connotation. It's important to choose the most appropriate synonym based on the tone, context, and purpose of the text to ensure the meaning is accurately conveyed.