By using db<>fiddle, you agree to license everything you submit by Creative Commons CC0.
CREATE TABLE #indebtedness (call_case CHAR(10), date1 DATETIME, date2 DATETIME, date3 DATETIME);
INSERT #indebtedness VALUES ('Key1', '2019-10-30', '2019-11-30', '2019-10-25');
INSERT #indebtedness VALUES ('Key2', '2019-10-20', '2019-10-30', '2019-10-15');
INSERT #indebtedness VALUES ('Key3', '2019-11-11', '2019-10-29', '2019-10-30');
INSERT #indebtedness VALUES ('Key4', null , '2019-10-29', '2019-10-13');
SELECT
call_case,
CASE WHEN date1 > date2 AND date1 > date3
THEN date1
WHEN date2 > date3
THEN date2
ELSE date3 END AS [Latest Date]
FROM #indebtedness;
| call_case | Latest Date |
|---|---|
| Key1 | 2019-11-30 00:00:00.000 |
| Key2 | 2019-10-30 00:00:00.000 |
| Key3 | 2019-11-11 00:00:00.000 |
| Key4 | 2019-10-29 00:00:00.000 |