Based on the info you are providing, you are entering this rent in the appropriate area. The reason why this is not making any difference is that you probably have a Net business loss prior to claiming this expense. You should be aware that you cannot increase or create a business loss by claiming office in the home expenses. Any amounts not deductible in this regard because of this restriction can be carried forward and applied against your Net business income in a future year. For more info please see http://www.cra-arc.gc.ca/tx/bsnss/tpcs/slprtnr/rprtng/t2125/ln9945-eng.html
