How to pass output of one stored procedure to the input of another I have a stored procedure which outputs @billingInvoiceIDOut. I want to use it as input in my next stored procedure. Can I just do in my second stored procedure 

INSERT INTO table ( billingID ) VALUE (@billingidout)


My first stored procedure:

BEGIN
    BEGIN TRANSACTION 
    BEGIN TRY
        SET NOCOUNT ON;
        IF NOT EXISTS(SELECT billingInvoiceID 
                      FROM tblBillingInvoice 
                      WHERE billingInvoiceID = @billinginvoiceID)
        --  IF @billinginvoiceID = NULL
        BEGIN
            INSERT INTO [dbo].[tblBillingInvoice
                (invoicenumber,versionnumber,patientID,date,
                officeID,userID,[tblBillingInvoice].status)
            VALUE ((SELECT IDENT_CURRENT('tblbillingInvoice')),1,@patientID,GETDATE(),
                    @officeID,@userID,1)
            SET @billingInvoiceIDOut =  (SELECT IDENT_CURRENT('tblbillingInvoice')) 
        END
    END TRY


or do I have to pass this parameter in exec statement as input, as I am running both stored procedures in one master stored procedure?
You must pass the value from the first SP to the second via a variable local to the master SP.  The bare bones of the code will look something like this:

create master_sp
..
declare @LocalVariable int;

exec first_sp
    @sp_parameter = @LocalVariable OUTPUT;

exec second_sp
    @sp_input = @LocalVariable;