In many countries, particularly in the UK and Commonwealth countries, someone with an honours degree might be addressed informally as "Mr./Ms./Mx. [Surname]" or formally as "Mr./Ms./Mx. [Surname], BA (Hons)" or "Mr./Ms./Mx. [Surname], BSc (Hons)," etc., replacing "BA" or "BSc" with the appropriate undergraduate degree abbreviation.
However, an honours degree itself *does not* automatically confer a professional title like "Doctor" (Dr.) or "Professor." Those titles are earned through postgraduate study (PhD or equivalent) or appointment to a professorial position, respectively.
Therefore, the best way to address someone with an honours degree is to use the standard Mr./Ms./Mx. [Surname] unless you know their professional title from other achievements. Including the degree abbreviation (e.g., BA (Hons)) is permissible in formal settings but might be considered excessive in casual contexts.