Using nested IF condition

I am making a vb.net project using SQL-SERVER at back end. Since SQL queries are lengthy i have to use STORED-PROCEDURE.. 

Following condition have to be tested in T-SQL. But my program frequently gives error ''INCORRECT SYNTAX NEAR BEGIN''

How can nested loop be used to execute following condition without error..

 if @commissiontypee!=@commissiontypee1 or @commissionamountt!=@commissionamountt1
        (
            begin
                if exists (select debit from tblledger where passportnumber=@passportnumberr and (typenumber=2 or typenumber=3)
                    (
                        begin
                        update tblledger set debit=@commissionamountt, typenumber=@typenumberr where ( passportnumber=@passportnumberr and (TypeNumber='2' or TypeNumber='3'))
                        set @initialdate= (select top(1) datetimer from tblledger where passportnumber=@passportnumberr and (typenumber=2 or typenumber=3))
                        set @datedifferences=datediff(day,@initialdate,getdate())
                            if @commissiontypee!=@commissiontypee1
                            (
                                begin
                                insert into tbllogfiles (OnDate,What,OfPassportnumber,ToValue,ChangedFrom,aftertime)values(getdate(),'Commission and ""COMMISSION-TYPE"" changed',@passportnumberr,@commissionamountt,commissionamount,@datedifferences)    
                                end
                            else
                                begin
                                insert into tbllogfiles (OnDate,What,OfPassportnumber,ToValue,ChangedFrom,aftertime)values(getdate(),'Commission changed',@passportnumberr,@commissionamountt,commissionamount,@datedifferences)    
                                end
                            )
                        )
                    else
                        (
                        begin 
                            if @commissiontype=0
                            --condition
                            insert into tblledger (passportnumber,datetimer, typenumber,debit) values (@passportnumberr,getdate(),2,@commissionamountt)
                            else
                            --condition
                            insert into tblledger (passportnumber,datetimer, typenumber,debit) values (@passportnumberr,getdate(),2,@commissionamountt)
                        end
                        )

            end
        )

Regards 

Saurav Gautam