If purchased for your business, you may deduct the cost of office expenses from your taxable income. Office expenses would include items such as pen, paper and toner.
If you purchase an asset such as a desk, chair or computer, do not include as a business expense but communicate that information to your tax preparer. Assets need to use the Capital Cost Allowance system and will be 'depreciated' over time. The time/percentage used to depreciate the asset varies depending on the asset itself. If there is personal use of that item (eg laptop), you will have to determine a rate to use that reflects the actual business time used.