Income Tax Folio S1-F5-C1, Related Persons and Arm’s Length

Under the Canadian Income Tax Act, two parties are treated as related persons and dealing at non-arm’s length whenever they fall into one of the categories set out in section 251. Related people are automatically deemed not to deal at arm’s length, no matter how fair their deal actually was.¹ That label carries real consequences: forced fair-market-value pricing under section 69, income attribution back to the transferor, and, in some cases, tax paid twice on the same economic gain. The Canada Revenue Agency’s Income Tax Folio S1-F5-C1 is the technical guide that walks through which relationships trigger this treatment and when strangers can still get caught by the same rules.²

Who the Act Treats as Related

Section 251(2)(a) lists three ways two individuals become related: blood relationship, marriage or common-law partnership, and adoption.¹ If the connection exists, section 251(1)(a) automatically deems the parties to be dealing not at arm’s length. Nobody has to prove that the family tie actually shaped the transaction. The relationship alone is enough.

Blood relationship is narrower than most people expect. Section 251(6)(a) covers only the direct parent-child line (including grandchildren and great-grandchildren) and siblings.¹ The statute says “brother and sister” without distinguishing full from half, so both are in.

Adoption is treated the same as biology. Section 251(6)(c) covers both legal adoption and de facto adoption, where a child has been raised as another person’s child even without a court order.¹ Once that relationship is in place, an adoptive parent and child are related for every purpose of the Act.

Relatives Who Are Not “Related”

Here is where readers get surprised. The CRA folio states plainly that your aunt, uncle, niece, nephew, or cousin is not connected to you by blood, marriage, or adoption for purposes of the Act.² Selling a cottage to your cousin is technically at arm’s length under the automatic rules. That doesn’t guarantee arm’s length treatment, though. The CRA can still apply the factual test discussed further down if the circumstances point the other way, and a niece or nephew you legally adopt becomes your child, at which point the exclusion no longer helps.

Marriage, Common-Law, and What Happens After a Breakup

Marriage extends the related-person circle well past the couple. Section 251(6)(b) makes you connected by marriage to your spouse and to everyone related by blood to your spouse.² Your spouse’s parents, siblings, children, and grandchildren are all related to you.

Common-law partnerships work the same way once the threshold is met. The CRA treats you as living common-law after you have lived with someone in a conjugal relationship for at least 12 continuous months.³ From that point on, your partner’s blood relatives are your related persons too.

A breakup doesn’t sever the status immediately. The CRA considers you separated only after you have lived apart from your spouse or partner for at least 90 days because of a breakdown in the relationship.³ Living apart for work, school, or health doesn’t count. Once the 90 days are complete, the effective separation date reaches back to the first day apart. The income attribution rules between spouses stop applying during periods when you are living separate and apart due to a relationship breakdown.

Related Corporations and Control

The concept extends into the corporate world through control. Under section 251(2)(b), a corporation is related to the person who controls it, to any member of a related group that controls it, and to anyone related to those people. A related group is a group in which every member is related to every other member.¹

Two corporations are related to each other if the same person or group controls both. The rule also catches the case where each corporation is controlled by a different person and those two people are related. A husband’s company and a wife’s company are therefore related to each other, and every transaction between them is automatically non-arm’s length.¹

Control has two forms. De jure control is ownership of more than 50% of the voting shares and the ability to elect the board. De facto control, defined in section 256(5.1), is broader: a corporation is controlled by a person who has any direct or indirect influence that, if exercised, would result in control in fact.⁴ A lender who could call a loan and shut the business down, or a customer who accounts for nearly all its revenue, can hold de facto control without owning a share.

There is one carve-out. If the corporation and the alleged controller deal at arm’s length and the influence flows from a franchise, license, supply, or similar commercial agreement designed to govern how a business is run, that agreement alone does not create de facto control.⁴ An ordinary franchise arrangement, on its own, won’t make franchisor and franchisee related persons.

Trusts

Trusts sit in their own corner because they mix control with beneficial ownership. The Act deems a trust to be an individual for purposes of section 251, so the related-person rules can apply to it directly.²

Under section 251(1)(b), a taxpayer and a personal trust are deemed not to deal at arm’s length if the taxpayer, or someone who does not deal at arm’s length with the taxpayer, is beneficially interested in the trust.¹ Two personal trusts become non-arm’s length with each other when the same person is a beneficiary of both, or when the beneficiaries of the two trusts do not deal at arm’s length with each other.²

Between a trust and its settlor, the general presumption is non-arm’s length. That presumption can be rebutted only if the trustee is a professional trustee such as a public trust company and the settlor has given up all influence over how the trust is managed.² Keeping any degree of influence over the trustee keeps the non-arm’s length status in place.

When Unrelated Parties Are Still Non-Arm’s Length

Even without a family, corporate, or trust connection, the CRA can find that a transaction was not at arm’s length. Section 251(1)(c) makes it a question of fact for every party who isn’t automatically related.¹

The folio points to three criteria the courts have used:²

A common mind directs the bargaining for both sides.
The parties act in concert, with highly interdependent conduct on a transaction of mutual interest, and no truly separate interests driving the negotiation.
One party holds de facto control through excessive or constant advantage, authority, or influence over the other.

The de facto control point reaches further than it looks. The courts have held that the influence doesn’t need to actually be exercised. The ability to exert it is enough. A sole supplier controlling all of a company’s inventory, or a creditor holding debt large enough to force the borrower’s hand, can end up in a non-arm’s length relationship without owning a share or being on the family tree.

What the Non-Arm’s Length Label Costs

The practical bite lives in section 69 of the Income Tax Act. It forces fair market value into non-arm’s length transactions whether the parties used it or not, and it works asymmetrically.

Sell property to a non-arm’s length person for less than fair market value and you are deemed to have received proceeds equal to fair market value. You pay tax on the higher amount even though you received less money. Buy property from a non-arm’s length person for more than fair market value and your cost base is cut down to fair market value. You overpaid, and none of the excess helps you at tax time.⁵

The adjustment on one side of the deal doesn’t automatically flow to the other. Say you sell a rental property worth $300,000 to your daughter for $200,000. You are deemed to have sold for $300,000 and pay tax on the full gain from your original cost. Your daughter’s cost base stays at $200,000. When she eventually sells, the same $100,000 gap gets taxed a second time in her hands.

Section 69 also catches gifts. Transfer property to any person by way of gift and you are deemed to have received fair market value; the recipient is deemed to have acquired it at fair market value.⁵ Gifts cannot be used to park accrued gains with someone else and defer the tax.

Income Attributed Back to You

Non-arm’s length status doesn’t only reprice transactions. It can also send income back to the transferor. Sections 74.1 and 74.2 exist to shut down income splitting between related parties, and they catch arrangements many families assume are routine.

Transfers to a Spouse or Common-Law Partner

Transfer or lend property to your spouse or common-law partner and any income or loss from that property is attributed back to you and taxed in your hands.⁶ Capital gains and losses on the property come back to you as well. The rule applies whether the transfer is direct, through a trust, or by any other means, and it applies to someone who becomes your spouse after the fact. Attribution continues while you are resident in Canada and the recipient remains your spouse or partner, and it pauses during any period you are living apart because of a relationship breakdown.

One common workaround is to lend money to a spouse at the CRA’s prescribed interest rate rather than gift it. For the first two quarters of 2026, the prescribed rate used to calculate taxable benefits on low-interest and interest-free loans is 3%.⁷ If the spouse actually pays the interest by January 30 of the following year, the attribution rules don’t apply. Miss that payment and the arrangement collapses retroactively.

Transfers to Children Under 18

Transfer or lend property to a child under 18 who does not deal at arm’s length with you, or who is your niece or nephew, and any income or loss from the property is attributed back to you until the child turns 18.⁶ Unlike the spousal rule, capital gains realized by the child on the transferred property are generally not attributed back. That gap creates a planning opportunity: property that generates mostly capital gains rather than interest or dividends can be more tax-efficient held by a minor. The same prescribed-rate loan escape valve is available, and the attribution rules also catch indirect arrangements including back-to-back loans through a third party, loan guarantees, and transfers into a trust for the child.

Cross-Border Transactions

When non-arm’s length transactions cross international borders, a separate regime applies. The CRA requires contemporaneous documentation showing you made reasonable efforts to use arm’s length prices in your cross-border dealings. The documentation isn’t filed with the return, but the CRA can request it at any time and you have three months to produce it. If the CRA adjusts your transfer prices and you haven’t made reasonable efforts, the penalty is 10% of the adjustment. Taxpayers with non-arm’s length transactions involving non-residents must also file Form T106 as an annual information return.⁸

1
Department of Justice Canada. Income Tax Act – Section 251
2
Canada Revenue Agency. Income Tax Folio S1-F5-C1, Related Persons and Dealing at Arm’s Length
3
Canada Revenue Agency. Marital Status
4
Department of Justice Canada. Income Tax Act – Section 256
5
Department of Justice Canada. Income Tax Act – Section 69
6
Department of Justice Canada. Income Tax Act – Section 74.1
7
Canada Revenue Agency. Interest Rates for the First Calendar Quarter
8
Canada Revenue Agency. Transfer Pricing