Dual-listed Canadian companies trade simultaneously on a TSX in CAD and a US exchange in USD. The textbook says the prices should match after FX. They almost never do. Here's why — and why most of the visible spread isn't actually tradeable.
If TD Bank trades at CAD $84.20 on the TSX and USD $61.80 on the NYSE, and the spot CAD/USD rate is 0.7350, the implied US price of the Canadian leg is:
The US leg is at $61.80, so the implied US price is 0.15 cents above the actual US price. As a percentage:
In a textbook frictionless market, an arbitrageur sells the expensive leg and buys the cheap leg until the spread closes. In reality, that 0.146% spread is well inside the no-arbitrage band. The interesting question is: at what spread does it become tradeable?
Five real costs eat the spread before you ever see a profit:
| Cost | Typical magnitude | Notes |
|---|---|---|
| Bid-ask spread, both legs | 0.05% — 0.50% | Wider on TSX-V juniors. Best on TSX/NYSE for the Big Five banks. |
| FX spread (the broker's quote) | 0.30% — 1.50% | Retail brokers can charge much more than the interbank rate. This is usually the biggest hidden cost. |
| Borrow cost on the short leg | 0.5% — 25% APR | Hard-to-borrow names eat the spread fastest. |
| Withholding tax on dividends | 15% — 25% on the wrong side | Holding period matters. Don't be the one paying foreign withholding. |
| Settlement & transfer fees | $0 — $50 per transfer | Some brokers waive; others don't. Read the fee schedule. |
Add it up. For a typical retail account, the total cost stack is 0.5% to 2.5% on a round trip. A 0.15% headline spread doesn't survive contact with the fee schedule.
The spread widens when:
A useful refinement is the volume ratio between the two legs. If the Canadian leg's volume normally runs 30% of the US leg's, and today it's running 90% with the spread widening, that's a sign of one-sided flow on the TSX side. Our Cross-Border Arb engine reports volume divergence as a secondary indicator next to the spread.
The Cross-Border Arb panel takes a CA ticker (e.g. SU.TO) and its US counterpart (SU), pulls live quotes for both legs (delayed up to 15 minutes), pulls the live FX rate, computes the FX-adjusted spread plus the volume divergence ratio, and prints the result alongside the FX rate used so you can audit the calculation. It does not tell you to trade. It does not factor in your specific broker's fee schedule, borrow availability, or tax treatment — those are inputs only you have. We surface the spread as a research output; you decide whether the post-cost spread is interesting.
Worth saying explicitly: arbitrage at retail scale on dual-listed Canadian names is rare. The market makers on both sides have far better latency, lower FX spreads, and tighter borrow than retail brokers. The retail-friendly use of this tool is research and timing — e.g. “CA leg is 0.4% rich vs US, and Canadian volume is unusually high — what's driving that?” — not actual cross-border arbitrage execution.
The Canada-US tax treaty under USMCA reduces dividend withholding on qualifying retirement accounts. Holding the US leg of a dual-listed Canadian dividend payer in a TFSA carries 15% US withholding. Holding it in an RRSP is treaty-exempt. This single decision often dwarfs the spread itself in long-run after-tax return. We don't model your tax situation — that's between you and your accountant — but cross-border investors should know the structure.