Matching Totals Once Using Filters

Thank you all - for now I have gone with ...

This is because SUMX did not want to work and repeated the same number all the way down however I will go back but assume I could get a couple of missed numbers for now.

Sum Project Billed Milestones = 
CALCULATE(
    SUM(Autotask_ContractMilestones_Billed[amount]),
    FILTER(
        DISTINCT(Autotask_ContractMilestones_Billed[contractID]),
        Autotask_ContractMilestones_Billed[contractID] = Autotask_Projects[contractID]
    )
)

I will also have a look at the schema option which seems to be a good way forward too.

Thanks

T