That depends on whether you are a salaried or commission employee. It also depends on whether your employer requires you to pay the expenses to earn employment income. In that case, salaried employees can claim accounting and legal fees, allowable motor vehicle expenses, parking costs, supplies, travelling expenses, work space in the home, salaries paid to a substitute or assistant, and office rent. In addition, commission employees can claim advertising and promotion expenses, capital cost allowance, entertainment, food, beverages, and lodging. Special rules apply to forestry workers, transport employees, musicians, artists, and tradespersons (e.g. apprentice vehicle mechanics).
See T777 - Statement of employment expenses for more details.
Can I claim common, everyday items as expenses?
Generally, no. CRA does not allow you to claim things like groceries, kosher or diet foods, vitamin supplements (unless prescribed by a doctor), laundry or dry-cleaning, work clothes, hair cuts, house-keeping, or travel to and from work.