Consultant cross-border tax: US engagements without a surprise US filing

The starting position: no US office, no US federal tax

Under the Canada–US tax treaty's business profits article, a Canadian consulting corporation with no fixed place of business in the US generally owes no US federal income tax on fees earned from US clients, even when the client is a large US company paying in USD. In practice, the client's accounts payable team will still ask for a completed W-8BEN-E before the first payment, so their system does not apply default 30% withholding. On the Canadian side, those fees are usually zero-rated for GST/HST as an export of services — you charge 0% but still recover input tax credits on your Canadian costs, and the sales still count toward the $30,000 small-supplier threshold.

On-site days: when the treaty's services clause kicks in

The protection above assumes the work happens from Canada, or on short US visits. It weakens once a consultant spends extended stretches physically working at a US client site. The treaty includes a specific services permanent establishment test: broadly, spending 183 days or more in the US within any 12-month period on the same or a connected project can create a deemed PE even without a fixed office — at which point the client's fees tied to that work become taxable in the US, and a US corporate tax filing follows. Firms running a long embedded engagement — a transformation program, an interim-management assignment — should count on-site days across the whole engagement, not per trip, well before the threshold is close.

State tax does not wait for a federal PE

Even short of a federal services PE, individual US states are not bound by the Canada–US treaty and can apply their own nexus rules based on physical presence alone. A consultant working on-site for a few weeks in a state with an aggressive nexus standard can trigger a state income or franchise tax filing obligation that exists independently of the federal treaty position. A number of states also require withholding on payments to non-resident service providers for work performed in-state — a state-by-state mirror of the concept behind Canada's own Regulation 105 withholding on non-residents working here, just administered one state at a time rather than federally. We check the specific states involved before a long on-site assignment is confirmed, not after the client's accounts payable team asks why they withheld part of the invoice.

• Short client visits — a few days for a workshop or kickoff — rarely create exposure on their own.
• Extended embedded assignments in one state deserve a nexus check before the contract is signed, not during it.
• Multi-state engagements compound the tracking problem — days can add up across states differently than they add up federally.

Sending an employee, rather than yourself, on an extended US assignment adds a workers' compensation question most firms only think about once someone gets hurt. WSIB coverage generally continues for an Ontario-based employee on a temporary out-of-country assignment, provided the posting is genuinely temporary and the employment relationship stays based in Ontario — worth confirming with WSIB directly before a long embedded placement, not after.

US travel expenses in the Canadian books

Meals, hotels, and incidentals for US assignments are ordinary deductible business expenses in Canada, converted to CAD on the corporation's books, but the reasonableness of a flat per-diem policy is easier to defend when benchmarked against a published reference point rather than picked arbitrarily. Published US government per-diem rates by city are a common, defensible benchmark for what a reasonable daily allowance looks like for the location in question, even though your corporation is not bound by them. Keeping a simple day-count log by state and by project — not just by trip — is the single habit that makes both the PE analysis and the state nexus check straightforward when the numbers are needed.

Don't overlook T1135 on the corporate side

A consulting corporation that keeps a USD bank account or carries outstanding US receivables is holding specified foreign property, and once the combined cost of that property exceeds $100,000 CAD at any point in the year, a T1135 foreign income verification return is required alongside the T2. Growing US-facing practices often cross this threshold quietly as receivables build up, and the penalties for a missed T1135 are separate from, and can exceed, any penalty tied to the income itself. We check this every year a corporation holds meaningful USD balances, not only in the year it seems obviously large.

Source: IRS — About Form W-8BEN-E.