A growing IT consulting firm that started with domestic subcontractors eventually brings in an offshore developer for a specialized project, or a US-based contractor for a client engagement that needs someone physically closer to the client. The invoice looks like any other subcontractor invoice, but the tax mechanics behind it are different: withholding tax, non-resident information reporting, and GST/HST all follow separate rules once the vendor is outside Canada.
This builds on subcontractor expenses for IT consulting firms, which covers T4A reporting, GST/HST, and project tracking for domestic subcontractors. Everything in that guide still applies to a firm’s Canadian resident subcontractors. This guide covers what changes when the subcontractor or vendor is not a Canadian resident.
Regulation 105 Withholding
CRA’s Regulation 105 withholding requirement requires a payer to withhold 15% from payments to a non-resident for services rendered in Canada, remitted to CRA, regardless of whether the non-resident ultimately owes Canadian tax on the income. This is a withholding-at-source mechanism, not a final tax determination, and the non-resident can later file a Canadian return to reconcile the actual liability.
The trigger is where the services are physically performed, not where the non-resident is a tax resident or where the paying firm is located. An offshore developer working from their home country, never setting foot in Canada, is generally outside Regulation 105 because the services are not rendered in Canada. The same developer flown in for a two-week on-site engagement at a Canadian client’s office changes the analysis for that period of work.
A consulting firm bringing in non-resident help should confirm, before the engagement starts, whether any part of the work will be physically performed in Canada. That single fact determines whether Regulation 105 withholding needs to be built into the payment terms from the outset, since retroactively withholding from an already-paid invoice is a harder problem than building it into the original contract.
T4A-NR and Non-Resident Reporting
Where withholding does apply, or where a non-resident is paid for services connected to Canada, T4A-NR reporting is the non-resident counterpart to the domestic T4A box 048 reporting covered in the subcontractor expenses guide. The reporting and withholding questions travel together in most cases: if Regulation 105 withholding was required, T4A-NR reporting generally follows.
A firm using non-resident subcontractors should track residency status, where services are physically performed, and whether any withholding was applied, as a standard part of onboarding a new offshore or foreign vendor, the same way GST/HST registration status is tracked for domestic subcontractors.
GST/HST on Foreign Vendor Invoices
GST/HST generally applies to taxable supplies made in Canada. A non-resident vendor with no presence in Canada, supplying services from outside the country, often falls outside the scope of GST/HST the way a domestic subcontractor invoice does not. But self-assessment obligations can apply to a Canadian business receiving certain supplies from a non-resident, meaning the absence of GST/HST on the vendor’s invoice does not always mean no GST/HST consideration applies to the transaction at all.
This is the opposite direction of the more commonly discussed non-resident GST/HST question, where a non-resident vendor sells into Canada and may need to register and collect GST/HST themselves. A consulting firm paying a foreign vendor is on the receiving end of the supply, and the analysis depends on the type of service purchased and how it is used in the firm’s own business, not on a single blanket rule.
US Contractors and W-8BEN Documentation
A US-based contractor paid by a Canadian consulting firm sits in a mirror-image position to the W-8BEN and W-8BEN-E documentation covered elsewhere for Canadian contractors receiving US client income. In that direction, a Canadian contractor completes a W-8BEN or W-8BEN-E for a US payer to establish non-US-resident status under the US tax system.
When a Canadian firm is the one paying a US-based subcontractor, the relevant documentation and withholding questions sit on the Canadian side under Regulation 105 and T4A-NR, not under the US W-8 system, since the US contractor is being paid by a Canadian payer for the Canadian analysis. A firm juggling both directions, paying US subcontractors and billing US clients, needs to keep the two documentation flows separate rather than treating one W-8 form as covering both relationships.
Building This Into Vendor Onboarding
The practical fix is treating non-resident status as a standard onboarding question, alongside the checks already applied to domestic subcontractors in subcontractor expenses for IT consulting firms. Before the first invoice is paid, a firm bringing on any subcontractor or vendor outside Canada should confirm: residency status, where the work will be physically performed, whether any part of the engagement involves in-Canada presence, and what documentation the arrangement requires on both the Canadian and, where relevant, the foreign side.
Retrofitting withholding onto an invoice already paid, or reconstructing a non-resident subcontractor’s work location months after an engagement ended, is a materially harder problem than confirming these facts at the start of the relationship.
Common Mistakes
Assuming “offshore” always means no Canadian tax consequences. The physical-presence test, not the vendor’s home country, drives the Regulation 105 and T4A-NR analysis. An offshore vendor who does any work on Canadian soil changes the picture for that portion of the engagement.
Treating GST/HST as automatically inapplicable to foreign invoices. Self-assessment rules can still apply depending on the supply. The absence of GST/HST on a foreign vendor’s invoice is not the end of the analysis.
Confusing the US W-8BEN direction. A form a Canadian contractor gives a US client does not answer the separate question of what a Canadian firm needs when it pays a US-based subcontractor.
Not documenting work location at the time of engagement. Confirming where services were physically performed becomes much harder to reconstruct after the fact than to record at the outset.
Related Guides
- Subcontractor Expenses for IT Consulting Firms covers T4A, GST/HST, and project tracking for domestic subcontractors.
- W-8BEN and W-8BEN-E for Canadian IT Contractors covers the mirror-image documentation for Canadian contractors paid by US clients.
- Employees vs. Subcontractors in a Consulting Firm covers the underlying worker classification question that applies before residency and withholding are considered.
If your firm is bringing on an offshore developer or a US-based subcontractor and has not confirmed the withholding and reporting position, that is worth reviewing before the first invoice is paid.
Get in touch to talk through non-resident subcontractor and vendor arrangements.