Report Builder functions - Sum function in a paginated report (Report Builder)
Applies to: 
Microsoft Report Builder (SSRS)
Power BI Report Builder
Report Designer in SQL Server Data Tools
Returns the sum of all the non-null numeric values specified by the expression, evaluated in the given scope in a paginated report.
Note
You can create and modify paginated report definition (.rdl) files in Microsoft Report Builder, Power BI Report Builder, and in Report Designer in SQL Server Data Tools.
Syntax
Sum(expression, scope, recursive)
Parameters
expression
(Integer or Float) The expression on which to perform the aggregation.
scope
(String) Optional. The name of a dataset, group, or data region that contains the report items to which to apply the aggregate function. If scope is not specified, the current scope is used.
recursive
(Enumerated Type) Optional. Simple (default) or RdlRecursive. Specifies whether to perform the aggregation recursively.
Return Type
Returns a Decimal for decimal expressions and a Double for all other expressions.
Remarks
The set of data specified in the expression must have the same data type. To convert data that has multiple numeric data types to the same data type, use conversion functions like CInt, CDbl or CDec. For more information, see Type Conversion Functions.
The value of scope must be a string constant and can't be an expression. For outer aggregates or aggregates that do not specify other aggregates, scope must refer to the current scope or a containing scope. For aggregates of aggregates, nested aggregates can specify a child scope.
Expression can contain calls to nested aggregate functions with the following exceptions and conditions:
Scope for nested aggregates must be the same as, or contained by, the scope of the outer aggregate. For all distinct scopes in the expression, one scope must be in a child relationship to all other scopes.
Scope for nested aggregates cannot be the name of a dataset.
Expression must not contain First, Last, Previous, or RunningValue functions.
Expression must not contain nested aggregates that specify recursive.
For more information, see Aggregate Functions Reference (Report Builder and SSRS) and Expression Scope for Totals, Aggregates, and Built-in Collections (Report Builder and SSRS).
For more information about recursive aggregates, see Creating Recursive Hierarchy Groups (Report Builder and SSRS).
Examples
A. Sum of line item totals
The following two code examples provide a sum of line item totals in the Order group or data region.
=Sum(Fields!LineTotal.Value, "Order")
' or
=Sum(CDbl(Fields!LineTotal.Value), "Order")
B. Maximum value from all nested regions
In a matrix data region with nested row groups Category and Subcategory, and nested column groups Year and Quarter, in a cell that belongs to the innermost row and column groups, the following expression evaluates to the maximum value from all quarters for all subcategories.
=Max(Sum(Fields!Sales.Value))