Superficial Loss Rule

Superficial loss rule is a Canada Revenue Agency (CRA) anti-avoidance rule, sometimes called the "30-day rule," that prevents you from claiming a capital loss while effectively keeping your position. It matters to anyone tax-loss harvesting Bitcoin or other crypto near year-end: the obvious move — sell at a loss to crystallize it, buy right back to stay exposed — is exactly the move the rule exists to deny. What follows is general educational information, not tax advice; crypto positions and account structures vary enormously, so consult a Canadian tax professional about your own circumstances.

When the rule applies

Set out in section 54 of the Income Tax Act, the rule is triggered when two conditions are both met: you (or an affiliated person) acquire the same or identical property within the period starting 30 days before and ending 30 days after a disposition at a loss, and you (or the affiliated person) still hold that property at the end of the window. Identical property means exactly that — bitcoin is identical to bitcoin regardless of which exchange or wallet it sits in. "Affiliated persons" include your spouse or common-law partner and a corporation you control, and the same denial logic extends to repurchases inside registered accounts such as your RRSP or TFSA. Selling bitcoin at a loss in a taxable account and buying it back inside your TFSA a week later can therefore trip the wire just as surely as rebuying in the same account — and in the registered-account case the outcome is worse, since a loss denied on a transfer into a registered plan is generally lost outright rather than deferred.

What happens to the denied loss

In the ordinary case, the loss is not gone forever. The denied capital loss is added to the adjusted cost base of the repurchased property, raising it above what you actually paid. The benefit is thereby deferred: when you eventually dispose of that property in a way that does not re-trigger the rule, the higher ACB produces a smaller gain or larger loss, and the tax effect you were denied earlier is recovered. Because Canada pools identical property into a single average-cost ACB, the mechanics interact directly with how filers compute their capital gains and losses on crypto — a denied loss quietly reshapes the average cost of everything you still hold.

Practical patterns for miners and hodlers

The simplest way to crystallize a genuine crypto loss is to avoid reacquiring the identical coin, in any account you or an affiliated person controls, until the full window has passed — in practice, waiting at least 31 days after the sale before rebuying. Watch the easy-to-miss triggers: recurring buy schedules that execute during the window, a spouse's purchase of the same coin, and — relevant to home miners — freshly mined coins landing in your wallet, since acquiring identical property is acquiring identical property regardless of how it arrives. Note also that the rule lives in the capital-gains regime; taxpayers whose crypto activity is treated as business income are under different rules entirely, and which regime applies is itself a facts-and-circumstances question.

The takeaway

The superficial loss rule does not forbid tax-loss harvesting — it disciplines it. Plan disposals with the 61-day span in mind (30 days before, the sale day, 30 days after), keep records of every acquisition date, and track your ACB carefully, because the denied-loss adjustment only helps you if it is actually recorded. For anyone stacking sats across multiple wallets, exchanges, and family accounts, clean records are what turn this rule from a trap into a scheduling detail.