Wash Sales and Superficial Losses: Two Loss-Denial Rules With Different Windows, and the Trade That Trips Both

Loss harvesting is where the two systems most often disagree about the same December trade, and the investor who checks one rule and not the other files a return that is wrong in the other country. The US wash sale rule: a loss on the sale of stock or securities is disallowed if, within the period beginning 30 days before the sale and ending 30 days after it (a 61-day window), the taxpayer acquires substantially identical stock or securities — or an option or contract to acquire them; the disallowed loss is not lost — it is added to the basis of the replacement shares, and the holding period of the sold shares tacks on, so the loss is deferred until the replacement shares are sold in a non-wash transaction; the rule applies to acquisitions by the taxpayer, by the taxpayer's spouse, and by a corporation the taxpayer controls, and — the trap with permanent consequences — to a repurchase inside the taxpayer's IRA or Roth IRA, where the disallowed loss is not added to the IRA's basis and is lost forever; "substantially identical" means the same security (or one convertible into it) — a different company in the same industry, or a different index fund tracking a similar index, is not substantially identical, which is the harvesting technique's basis; and the rule does not apply to cryptocurrency under current law (digital assets are not stock or securities — the crypto guide), or to commodities and foreign currency. Canada's superficial loss rule: a loss on the disposition of property is denied where, within the period beginning 30 days before and ending 30 days after the disposition, the taxpayer or an affiliated person acquires the same or identical property (a substituted property) and the taxpayer or affiliated person still owns it at the end of the period; the denied loss is added to the adjusted cost base of the substituted property (deferring, not eliminating, the loss) — except where the acquirer is the taxpayer's RRSP, RRIF, or TFSA, in which case the loss is denied and not added to anything (the registered plan has no cost base for the purpose), so the loss is lost permanently, mirroring the US IRA trap; "affiliated persons" is broad — the taxpayer, their spouse or common-law partner, a corporation controlled by either, a partnership of which they are a majority-interest partner, and a trust of which they are a majority-interest beneficiary (which sweeps in the RRSP, RRIF, TFSA, and RESP as trusts) — broader than the US's spouse-and-controlled-corporation list; "identical property" means property that is the same in all material respects — the same security, the same fund (a different fund tracking a similar index is not identical, so the swap technique works in Canada too), and, under the CRA's view, the same cryptocurrency (the superficial loss rule applies to identical crypto — the divergence from the US); and the rule applies to a partial repurchase proportionally (the denied portion of the loss is the fraction of the sold shares that were repurchased). The trades that trip both: selling at a loss in a taxable account and rebuying the same security within 30 days in any account of the taxpayer or spouse — denied in both countries, with the US adding the loss to basis and Canada adding it to the substituted property's ACB (and both losing it permanently if the repurchase was in a registered or IRA account); the trades that trip one: a loss harvested and rebought after 31 days — allowed in both (the windows are the same length); a loss on crypto sold and rebought within 30 days — allowed in the US, denied in Canada; a loss on a security rebought by the taxpayer's controlled corporation — denied in both; a loss on a security rebought by the taxpayer's adult child — allowed in both (children are not affiliated persons or wash-sale-covered relatives, though the US's related-party loss rules and Canada's attribution rules have their own reach); a loss on a security rebought inside the taxpayer's RRSP within 30 days — denied and lost in Canada, and — because the RRSP is a foreign account whose contents the US taxes only on distribution — the US wash sale rule's application to a repurchase in a foreign retirement plan is analyzed under the IRA rule by analogy, with most practitioners treating it as a permanent loss; a loss on a Canadian mutual fund replaced by a different fund with the same manager and mandate — not identical in Canada, not substantially identical in the US, allowed in both (and for a US person the PFIC regime's own rules govern the disposition anyway). The dual filer's routine: every loss trade is checked against both windows, both affiliated-person lists, and both property definitions; the denied loss is tracked to the substituted property's basis in each country's ledger separately (the US basis adjustment and the Canadian ACB adjustment are computed independently and may differ where the repurchase amounts differ); registered and IRA repurchases are avoided entirely in the window (the permanent-loss cases); and the replacement security is chosen to be non-identical in both countries' terms — a different fund tracking a comparable index, or a different company in the sector — which satisfies both rules and preserves the position. The foreign tax credit note: a loss denied in one country and allowed in the other creates a year-by-year mismatch — the country allowing the loss has lower tax that year, the country denying it has higher, and the credit runs on each year's numbers with the deferred loss surfacing later — the ordinary timing friction the double-tax guide describes, manageable when the ledgers are kept and confusing when they aren't.

Key takeaways

• Same window, different scope: both rules run 30 days before and after (61 days); the US covers stock and securities (not crypto); Canada covers identical property of any kind (crypto included).
• Who counts: US — you, your spouse, a corporation you control, and your own IRA (a permanent loss); Canada — you, your spouse, controlled corporations, majority-interest partnerships and trusts, including your RRSP, RRIF, TFSA, and RESP (a permanent loss for the registered plans).
• What happens to the loss: deferred into the replacement's basis (US) or the substituted property's ACB (Canada) — except registered-plan and IRA repurchases, where it is gone.
• Crypto diverges: harvest-and-rebuy is allowed in the US under current law and denied in Canada as a superficial loss.
• The replacement technique works in both: a different fund tracking a comparable index or a different company in the sector is neither substantially identical nor identical — the position is kept and the loss is preserved.
• Two ledgers: the basis and ACB adjustments are computed separately and may differ; the year-by-year mismatch where one country denies and the other allows is a credit-timing item, not an error.

The two-rule loss check

Before any loss sale: is the security or property being repurchased (by you, your spouse, a controlled corporation, or — for Canada — any affiliated trust including your registered plans) within 30 days before or after? If yes and identical/substantially identical: denied in both (or one, for crypto) — choose a non-identical replacement or wait 31 days. Never repurchase in the RRSP, TFSA, or IRA inside the window (permanent loss). After the trade: record the US basis adjustment and the Canadian ACB adjustment separately. A thirty-second check per trade that prevents the December harvest from becoming two amended returns.

Worked example

A dual citizen in Vancouver, married to a Canadian, harvests losses in December. Trade one: sells a Canadian bank stock at a loss in her taxable account and, ten days later, her husband buys the same stock in his TFSA. Canada: the husband is an affiliated person and the TFSA is an affiliated trust — superficial loss, denied, and because the acquirer is a TFSA, lost permanently. US: the spouse's acquisition triggers the wash sale rule — denied, and the loss is added to the basis of the husband's shares for US purposes (which, since he's not a US person, is academic — the loss is effectively lost for her US return too). A bad trade in both countries, for reasons each country's rule states differently. Trade two, corrected: she sells a Canadian index ETF at a loss and buys a different provider's ETF tracking a comparable but not identical index the same day. Canada: not identical property — the loss is allowed. US: not substantially identical — allowed (and, as a US person, the PFIC regime governs the disposition of the Canadian ETF, with her mark-to-market election making the loss computation its own exercise — the PFIC guides). Trade three: she sells a crypto position at a loss and rebuys it a week later. US: allowed — no wash sale rule for digital assets under current law; the loss offsets her US gains. Canada: superficial loss — denied, the loss added to the ACB of the repurchased units; her Canadian gain next year will be correspondingly smaller, and her ledger records both countries' treatment separately. Three December trades, five different answers across two countries, and one ledger that keeps them straight.

Official sources

Publication 550 explains the wash sale rules: a loss on the sale of stock or securities is not deductible where, within 30 days before or after the sale, the taxpayer acquires substantially identical stock or securities, with the disallowed loss added to the basis of the new stock, and with the rule applying to acquisitions by the taxpayer's spouse or by a corporation the taxpayer controls. — Internal Revenue Service, About Publication 550, Investment Income and Expenses, https://www.irs.gov/forms-pubs/about-publication-550

The CRA explains that a superficial loss can occur when a taxpayer disposes of property at a loss and, in the period beginning 30 days before and ending 30 days after, the taxpayer or an affiliated person acquires (or has the right to acquire) the same or identical property and still owns it 30 days after — with the denied loss usually added to the adjusted cost base of the substituted property. — Canada Revenue Agency, Capital losses and deductions, https://www.canada.ca/en/revenue-agency/services/tax/individuals/topics/about-your-tax-return/tax-return/completing-a-tax-return/personal-income/line-12700-capital-gains/capital-losses-deductions.html

Practitioner note

The two loss-denial rules share a window and disagree on everything inside it — scope, affiliated persons, crypto, and what happens to the loss — so a cross-border investor's December harvest is checked twice before every trade. Our two-rule check takes thirty seconds and prevents the permanent-loss cases (registered-plan and IRA repurchases) that no ledger can fix; the replacement technique — non-identical in both countries' terms — keeps the position and the loss, which is the whole point of harvesting.

See also: For selling a Florida home before or after a move back to Canada, see selling a Florida home before or after a move back to Canada; and browse every cross-border tax topic guide, organized by situation.

Next step

Fairlight prepares the cross-border loss-harvesting protocol — the two-rule pre-trade check against both windows, affiliated-person lists, and property definitions, replacement-security selection, and separate US basis and Canadian ACB ledgers for denied losses. See cross-border pricing or book a call.