UFN_REGISTRANT_CALCULATETOTALPAID

            create function dbo.UFN_REGISTRANT_CALCULATETOTALPAID
            (
                @ID uniqueidentifier = null
            )
            returns money
            with execute as caller
            as begin
                declare @TOTALPAID money = 0
                declare @TOTALREFUNDED money = 0

                select @TOTALPAID = coalesce(sum([REVENUESPLIT].[AMOUNT]),0)
                from dbo.[REVENUESPLIT]
                inner join dbo.[EVENTREGISTRANTPAYMENT] 
                    on [EVENTREGISTRANTPAYMENT].[PAYMENTID] = [REVENUESPLIT].[ID]
                where [EVENTREGISTRANTPAYMENT].[REGISTRANTID] = @ID

                select @TOTALREFUNDED = coalesce(sum([CREDITITEMS].[TOTAL]),0) 
                from dbo.[UFN_REGISTRANT_GETCREDITITEMS](@ID) [CREDITITEMS]

                return @TOTALPAID - @TOTALREFUNDED;
            end