partial month revenue allocation

Hi katzaway 
You can use a formula that checks if the current month (E4) is the same as the start or end month of the contract. If it is, then only allocate half of the monthly allocation. Otherwise, allocate the full amount.
Here’s an example approach formula:

=IF(OR(EOMONTH(E$4,0)=EOMONTH(Data[Start Date],0), 
EOMONTH(E$4,0)=EOMONTH(Data[End Date],0)), 
SUMIFS(Data[Monthly Allocation], Data[Client Name], $A5, Data[Start Date], "<="&E$4, Data[End Date],">="&E$4)/2, 
SUMIFS(Data[Monthly Allocation], Data[Client Name], $A5, Data[Start Date], "<="&E$4, Data[End Date],">="&E$4))

This formula checks if the current month (E4) is the same as the start or end month of the contract. If it is, it divides the monthly allocation by 2. If not, it uses the full monthly allocation. And I assumes that the start and end dates of the contract are always at the end of the month. If this is not the case, you may need to adjust the formula accordingly. Also, this formula does not account for multi-year deals where you need to show the last month to calculate 50% of year 1 and 50% of year 2. You might need to add additional logic to handle this scenario.
I hope this helps! Let me know if you have any other questions.