Speed up SUMX formula

Hi All,

I need help with speeding up a formula that doesnt sum up correctly, so have to use SUMX to get the correct total.

However this is so slow at loading it times out when on BI server

What i am trying to essentially do is work out customers that gave notice and sum the last 12 months worth of revenue linked to a different table. cannot do relationship between two tables on Account Id due to BI not allowing on Many-to-Many etc

Formula  below:

Terminated|Revenue|12m = 

VAR TermDate = 
    SELECTEDVALUE ( 'Revenue'[Account_Id]) 


VAR results = 
CALCULATE([Terminated|Revenue],  
      DATESINPERIOD ( 
        'Date'[Date],                 
        EOMONTH ( MAX ( 'Terminated|SF'[Notice]), 0 ), 
        -12,  MONTH),USERELATIONSHIP('Date'[Date],'Terminated|SF'[Notice]))


RETURN

results

the sumx and summarize formula:

Terminated|Revenue|12m2 = 

SUMX(
  SUMMARIZE('Terminated|SF',
    'Terminated|SF'[Account_Id],
    'Terminated|SF'[Account_Name],
    'Terminated|SF'[Notice]),
      'Terminated|SF'[Terminated|Revenue|12m])