Your result looks like ACTIVITY_DATE is stored as a string and is not truly a date.

If that's the case, you should be able to convert it from a string to a date for the evaluation.

   SELECT customer_no,
          tax_state,
          MAX(TO_DATE(activity_date, 'MM/DD/YYYY')) AS last_activity_date
     FROM table
    WHERE customer_no = '110913'
 GROUP BY customer_no, tax_state

@durette that’s true, the issue was with data type, 

Thanks for replying

@durette oops, i wanted to mark your answer as Best Answer and accidently clicked on my own…. now i can’t change it………. bummer

Done!