Inventory by subtracting the amount of incoming and outgoing

i want get Inventory by subtracting the amount of incoming and outgoing goods with stored procedure ,

i try get inventory from two parameter : @income - @outcome = inventory

USE [Bonakdar_DB]

GO

/****** Object:  StoredProcedure [dbo].[SP_Inventory]    Script Date: 06/11/2015 11:35:36 ?.? ******/

SET ANSI_NULLS ON

GO

SET QUOTED_IDENTIFIER ON

GO

ALTER PROCEDURE [dbo].[SP_Inventory]

AS

DECLARE @income INT = (select sum(Quantity) from View_Inventory where [Type_Bool] = 1 group by [Commodity_Id])

DECLARE @outcome INT = (select sum(Quantity) from View_Inventory where [Type_Bool] = 0 group by [Commodity_Id])

DECLARE @uotput TABLE (

    commo_Id int,

    nam nvarchar(20),

    quant int,

    uni nvarchar(50),

    typ nvarchar(10),

    dat datetime      )

INSERT @uotput 

SELECT [Commodity_Id], [Name], [Quantity], [Unit], [Type], [Date] FROM View_Inventory

BEGIN

SET NOCOUNT ON;

SELECT commo_Id, nam, quant, (@income - @outcome) AS inventory, uni, typ, dat FROM @uotput ORDER BY dat    

END

but display output table without inventory parameter and send error :

Msg 512, Level 16, State 1, Procedure SP_Inventory, Line 3

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

Msg 512, Level 16, State 1, Procedure SP_Inventory, Line 4

Subquery returned more than 1 value. This is not permitted when the subquery follows =, !=, <, <= , >, >= or when the subquery is used as an expression.

(4 row(s) affected)