Are classified ad purchases tax deductable?

Purchase costs of items reasonably connected with the operation of your business are an allowable business expense that you can deduct from your business income, although some items are required to be listed as fixed assets and depreciated at the rate specified by the CRA rather than counted as a one-time expense.

Better be able to justify how it is required for your business if audited.

Claim it through petty cash under advertising, maintenance or misc expense. Make handwritten receipt for $xx.xx, date and reason.

If it's an equipment I don't imagine it being hard to justify as business related and reasonable.

CRA reserves the right to disallow any expenses where you can't generate documentation. So if you won't be receiving a receipt, maybe you can save any texts or emails indicating you agreed to buy this thing for X dollars. In an audit, CRA won't check every line you put into your books. Usually they select big transactions or categories they deem more sensitive to abuse. So how you record it could matter. Like if you are lazy and bought 5 equipment and enter them all at once as one line, that could come back to haunt you.