In Ontario, small businesses can deduct a variety of expenses to lower their taxable income. Salaries and wages paid to employees are fully deductible, as are employer contributions to benefits like CPP and EI. Rent or lease payments for your business premises, including home office expenses, can also be deducted. Office supplies and equipment purchases, such as computers, printers, and software, are eligible for deductions. Utilities like electricity, heat, and internet used for business operations can be deducted proportionately if you work from home.

Vehicle expenses, including gas, maintenance, and insurance, can be partially deducted if you use your personal vehicle for business purposes. Advertising and marketing costs, such as online ads, print materials, and website expenses, are fully deductible. Professional fees for services like accounting, legal advice, and consulting are also eligible for deduction. Interest on business loans and related bank charges can be written off. Lastly, business travel expenses, including meals, accommodation, and transportation, are deductible, though some limitations apply to meal costs.

It's essential to keep accurate records and consult with a tax professional to ensure you claim all eligible deductions while complying with tax regulations.