Sum does not except 3 parameters

Hi RockyDylan !

When you want an aggregative function to perform a simple aggregation, it should only receive a single parameter - e.g. SUM([Sales]).

There are two primitives of when an aggregation function receives more than one parameter:

• Used as (SUM([Sales]),[Region]) - When "Region" is a filter for the items that have to be aggregated
• Used as AVG([Region]),SUM([Sales])) - When you want to get the average sum of each region

It seems that you're attempting to sum up two independent values - 

1. Sum of [total_client_facing_hours]
2. Sum of [total_capacity_hours_on_day]*0.36 with a filter of [work_department] and [work_title]

In this case, try using the following formula:

SUM([total_client_facing_hours])-(SUM([total_capacity_hours_on_day]),[department_filter],[title_filter])*0.36

RockyDylan ,

If you are trying to add 3 fields together, split the formula and use SUM function for each fields separately.

(sum([work_department]) + sum([work_title]) + sum([Total total_capacity_hours_on_day]))*0.36

-Hari

If you want to use a multi-pass aggregation here you could use this variant: 
sum([work_department],sum([work_title],[Total total_capacity_hours_on_day]*0.36))