Minimum value on most recent date per account MS ACCESS SQL
This would be a good place to use window functions if your RDBMS supports them. The example below is T-SQL so if you are not on SQL Server you may have to adapt the syntax and/or keywords.

Window Functions are ANSI Standard starting with SQL:2003, and as such you likely have access to them with any modern RDBMS. If you are on SQL Server read about their implementation of Window Functions here.

SELECT CHACCTBS, CHRQDATE, CHSCORE
FROM
(
    SELECT
         MIN(CHSCORE) OVER(PARTITION BY CHACCTBS) As CHACCTBS
        ,CHRQDATE
        ,CHSCORE
        ,ROW_NUMBER() OVER(PARTITION BY CHACCTBS ORDER BY CHRQDATE DESC, CHSCORE) As Limiter
    FROM RiskScore
) X
WHERE Limiter = 1


The subquery returns your MIN and other columns, and creates a filter by assigning row numbers by your partition and ordered by descending dates. You then take the first row of each partition in the WHERE clause.