There are expenses you incur to earn income that no named line on Form T2125 covers. Those go on line 9270, Other expenses — and you have to list them on the form with a description, so this is a named list rather than a catch-all.
What belongs here
The CRA names the more common ones.
Disability-related modifications. You can deduct eligible disability-related modifications made to a building in the year you paid them, instead of adding them to the capital cost of the building. Eligible changes include installing hand-activated power door openers, installing interior and exterior ramps, and modifying a bathroom, an elevator, or a doorway. You can also deduct what you pay to install or get disability-related devices and equipment, such as elevator car-position indicators, visual fire-alarm indicators, listening or telephone devices for people with a hearing impairment, and disability-specific computer software and hardware attachments.
Computer and other equipment leasing costs. If you lease computers, cellular telephones, fax machines, or other similar equipment, you can deduct the share of the lease costs that reasonably relates to earning your business income. The same goes for the share of cellphone air-time expenses that reasonably relates to earning your self-employment income.
Property leasing costs. Deduct the lease payments incurred in the year for property used in your business.
Convention expenses. You can deduct the cost of attending up to two conventions a year. The convention has to relate to your business or professional activity, and be held by a business or professional organization within the geographical area where the organization normally conducts its business. That second condition may not apply when an organization from another country sponsors a convention that relates to your business.
Allowable reserves. You can deduct an amount for a reserve, a contingent account, or a sinking fund, as long as the federal Income Tax Act allows it and the amount is reasonable.
Private health services plan (PHSP) premiums. These are premiums for a plan insuring you, your spouse or common-law partner, or a member of your household. You have to be actively engaged in your business on a regular and continuous basis, individually or as a member of a partnership, and there are income conditions and coverage conditions the CRA's page sets out in full. You cannot claim them if someone else deducted the amount, or if the premiums were claimed as a medical expense.
What does not belong here
Anything a named line already covers. Enter an amount on line 9270 only if you did not include it on a previous line. Rent, utilities, insurance and the rest each have their own line.
Equipment you bought rather than leased. If you buy a computer, a cellular telephone, a fax machine, or other such equipment, you cannot deduct the cost. It is capital property: the cost comes off over several years through capital cost allowance (CCA), and the interest on money you borrowed to buy it is deductible to the extent it relates to earning business income.
A leased passenger vehicle. Those lease costs are capped and claimed with the rest of your vehicle costs on line 9281, not here.
When a convention fee includes meals
Convention fees sometimes cover food, beverages, or entertainment without the organizer showing those amounts separately on your bill. When that happens, a set daily amount is subtracted from the total fee for each day the organizer provides them. That daily amount is treated as a meal and entertainment expense, so the meals limit applies to it and only half of it can be claimed. The CRA's page gives the amount.
Incidental items such as coffee and doughnuts at convention meetings or receptions are not food, beverages, or entertainment for this purpose.
What to keep
Keep a record of all your income and expenses, with the documents behind them. Because every amount on this line has to be listed with a description, the description you write is part of the record: name what it was and why the business needed it.
Keep the lease agreements, the convention registration and agenda, the insurer's statement for a PHSP, and the invoices behind any modification work.
Don't send them in with your return. Keep them in case the Canada Revenue Agency (CRA) asks to see them. Business records follow the same six-year retention rule as your personal documents.
Official CRA sources
Source: Canada Revenue Agency (canada.ca). Not tax advice.