Fourteen TSX names moved more than a percentage point in Wednesday's session. Allied Gold Corp led the losses, down 18.64 percent. Aecon Group fell 9.11 percent and Badger Infrastructure Solutions dropped 8.37 percent. Celestica lost 6.2 percent ahead of Microsoft and Meta earnings, and the two largest Canadian banks, TD and RBC, fell 3.2 and 3 percent respectively as higher bond yields pressured financials. Energy names moved the other way, with Canadian Natural Resources and Cenovus both up more than 4.5 percent on the day's crude oil spike.
For a client holding an embedded loss in a non-registered account, a session like this is not just a bad day. It is a specific, time-stamped planning opportunity, and one that comes with a rule advisors need to apply correctly or the loss disappears.
The 30 Day Rule That Turns a Loss Into a Cost Base Adjustment
Selling a security at a loss in a non-registered account creates an allowable capital loss, which can offset a taxable capital gain realized in the same year, be carried back up to three prior tax years, or carried forward indefinitely. That is the planning value in Wednesday's session for any client who has already realized gains elsewhere in 2026.
The mechanic that trips this up is the superficial loss rule. If the taxpayer, their spouse or common law partner, or a corporation they control buys back the identical security within 30 days before or 30 days after the sale, a 61 day window in total, the Canada Revenue Agency denies the loss. It is not lost entirely: it gets added to the adjusted cost base of the repurchased shares, deferring the benefit rather than eliminating it, but it does not offset this year's gain the way the client expects. A client who sold Allied Gold at Wednesday's close and wants to buy it back needs to wait out that window in every account they or an affiliated person controls, including a spouse's non-registered account.
This Only Works in Certain Accounts
Capital losses are a non-registered account and corporate investment account concept. RRSP, TFSA, FHSA, and RESP accounts do not recognize capital losses for tax purposes: a loss realized inside a registered account simply disappears, with no offsetting benefit. A CCPC's corporate investment account can harvest losses against corporate capital gains using the same superficial loss mechanics as an individual, which matters for incorporated business owner clients who hold a passive investment portfolio inside the corporation alongside their operating business.
The account distinction changes the conversation for a client holding the same stock across multiple accounts. A client who holds Aecon Group in both a non-registered account and a TFSA can only harvest the loss on the shares sold from the non-registered side, and buying back inside the TFSA within the 30 day window still triggers the superficial loss rule on the original sale, since the rule looks at repurchases across all accounts the taxpayer and affiliated persons control, not just the account where the sale occurred.
Wednesday's session, ranked by the size of the move, positive and negative, spans the fourteen TSX names that shifted by more than a percentage point.
Percentage moves are Wednesday's close versus Tuesday's close. Gold miners and infrastructure names led the declines while energy producers gained on the day's crude oil spike; financials fell on higher bond yields tied to the Fed's split decision.
The Window Does Not Wait for December
Tax loss selling is usually framed as a year end exercise, timed to the last trading days before the settlement deadline for that tax year. That framing misses that the superficial loss rule and the offsetting mechanic work identically in July. A genuine single session dip like Wednesday's, driven by a Fed decision and a fresh Middle East escalation rather than anything specific to Allied Gold or Aecon Group, is exactly the kind of drop that creates a harvesting opportunity most clients will not think to act on outside of the usual December conversation.
The complication is timing in the other direction. US equity futures were already higher Thursday morning on a strong Microsoft earnings report, and nothing about Wednesday's Fed dissents or the overnight strikes on Iran has been resolved to justify Wednesday's prices holding. If Thursday's session recovers even part of Wednesday's move, the specific price level that made harvesting the loss worthwhile starts to close. This is a call to make this week, not a note to revisit in November.