SQL Sum with MAX condition
What is the Claim table used for?

Well, you can try that:

select EmployeeClaimId, sum(Amount)
from ClaimStatus cs
join (
    select EmployeeClaimId, max(version) as version
    from ClaimStatus 
    group by EmployeeClaimId
    ) c on cs.EmployeeClaimId = c.EmployeeClaimId
        and cs.version = c.version