The small business deduction is the largest ongoing tax benefit an owner-operated Canadian company gets, and the one a buyer is most likely to price wrong. Income Tax Act section 125 turns on three questions: is the corporation a Canadian-controlled private corporation, is its income active business income, and what survives of its $500,000 business limit after two reductions computed on the target’s numbers, already fixed before you close.
Key takeaways
SECTION 01 OF 08
The marginal note on s. 125(1) is Small business deduction, and its words are narrower: “There may be deducted from the tax otherwise payable… by a corporation that was, throughout the taxation year, a Canadian-controlled private corporation… the corporation’s small business deduction rate… multiplied by the least of” three amounts.
Those three are ceilings and the lowest binds: (a) income “from an active business carried on in Canada”, net of losses; (b) taxable income, adjusted for foreign tax credits; (c) the business limit. An untouched $500,000 limit still yields little if (a) or (b) is what binds.
Subsection (1.1)(c) sets that rate at 19%, which is not the benefit. Under s. 123.4 a CCPC’s full rate taxable income excludes “the least of the amounts… determined under paragraphs 125(1)(a) to (c)”: deduction income does not also get the general rate reduction. The rate gap that leaves is worked out in the companion piece on associated corporations.
SECTION 02 OF 08
Section 125(7) defines a CCPC as “a private corporation that is a Canadian corporation” other than one “controlled, directly or indirectly in any manner whatever, by one or more non-resident persons, by one or more public corporations… or by any combination of them”, or one with a class of shares “listed on a designated stock exchange”. Paragraph (b) also gathers dispersed non-resident stakes into one notional holder.
A foreign strategic purchaser or a listed acquirer therefore removes the deduction at closing; Treadstone Law’s explainer confirms all three triggers. Note also throughout: an acquisition of control forces a deemed year-end, so the stub year before closing is tested against the vendor and the year after against the buyer — mechanics in the companion article.
SECTION 03 OF 08
The Act does not describe an active business; it subtracts two. “Active business carried on by a corporation means any business carried on by the corporation other than a specified investment business or a personal services business and includes an adventure or concern in the nature of trade.” A second definition adds “any income… pertaining to or incident to that business, other than income… from a source in Canada that is a property”: interest on an operating float is incidental, interest on a portfolio in the same company is not.
A specified investment business is one “the principal purpose of which is to derive income (including interest, dividends, rents and royalties) from property”. It escapes that label where “the corporation employs in the business throughout the year more than 5 full-time employees”, or where an associated corporation supplies services it would otherwise need more than five people for. Headcount belongs in diligence on any target with a rental arm.
A personal services business is one where the individual performing the services, or a person related to them, is a specified shareholder and would “reasonably be regarded as an officer or employee of the person… to whom… the services were provided but for the existence of the corporation”. Paragraph 18(1)(p) then denies every outlay except that person’s pay and benefits, certain selling costs and collection legal fees; s. 123.5 adds 5% of the income; s. 123.4(a)(iii) strips the general reduction.
Two deal patterns walk into it: a target whose revenue is one person’s services to one client, and a vendor who stays on as a consultant through their own corporation. CRA’s T2 guide lists everything that comes out of net income to get there, and puts a specified shareholder at “at least 10% of the issued shares of any class”. Treadstone Law covers active business income, the property test and the PSB rules without the statutory numbers.
SECTION 04 OF 08
Subsection 125(2): the limit “is $500,000 unless the corporation is associated… with one or more other Canadian-controlled private corporations, in which case… its business limit is nil”, restored only by the subsection (3) allocation agreement. Association is covered in the companion article.
Second, proration. Paragraph 125(5)(b): where a CCPC “has a taxation year that is less than 51 weeks, its business limit for the year is that proportion… that the number of days in the year is of 365.” An acquisition of control ends the taxation year, so both stub years of the closing year carry prorated limits.
Third: paragraph 125(5)(a) caps the limit for the later of two taxation years ending in one calendar year at the lesser of the two determinations, where the corporation is associated in both. A buyer who already owns a corporation and closes mid-year is in it. CRA names the filings: Schedule 23 for the allocation, Schedule 7 for a limit assigned in.
SECTION 05 OF 08
Subsection 125(5.1) decides how the two reductions interact, and one word does it: the limit “is the amount, if any, by which its business limit otherwise determined… exceeds the greater of” the two amounts. They do not stack — CRA says the same.
Paragraph (a) is A × B ÷ $90,000, where B is “0.225% × (C – $10 million)”. At $50 million of taxable capital B is exactly $90,000 and the limit is gone; it falls in a straight line from $10 million, a range CRA confirms (it was $10–$15 million before 7 April 2022). C is measured for “the preceding taxation year” — for a group, each member’s last year ending in the preceding calendar year.
Taxable capital is a balance-sheet measure. Under s. 181.2 capital includes “retained earnings, contributed surplus and any other surpluses”, “all loans and advances to the corporation” and debt “represented by bonds, debentures, notes, mortgages… or similar obligations”, less an allowance for shares of and loans to other corporations. A long-profitable target has been building that number for years, and acquisition debt pushed into it adds directly. Treadstone Law’s note on the grind gives the shape but no thresholds.
SECTION 06 OF 08
Paragraph 125(5.1)(b) is D/$500,000 × 5(E − $50,000), where E totals adjusted aggregate investment income “of the corporation, or of any corporation with which it is associated… for each taxation year… that ended in the preceding calendar year”. Five dollars of limit per dollar above $50,000, so it is gone at $150,000.
CRA’s Q&A on the 2018 change works it: $75,000 of such income in 2019 cut the 2020 limit to $375,000; add an associated corporation with $55,000 and 5($130,000 − $50,000) = $400,000 comes off, leaving $100,000. Use it for passive mechanics only: its taxable capital range, $10–$15 million, is out of date.
The measure is the aggregate investment income of s. 129(4) as adjusted by s. 125(7): gains on an active asset come out, dividends from connected corporations come out, specified investment business income goes in. Sell a redundant investment property the year before closing and the gain lands in E for the buyer’s first full year; sell operating premises used principally in the business and it may not. Subsection 125(5.2) shuts the obvious workaround. Treadstone Law’s article on it confirms the group is combined but gives no thresholds.
SECTION 07 OF 08
A buyer modelling after-tax earnings in Ontario runs two limits, not one. On taxable capital the province follows: CRA’s Ontario small business deduction page says the deduction “is phased out for CCPCs (including associated corporations) with taxable capital employed in Canada of more than $10 million in the previous tax year” and is “completely eliminated when the taxable capital is $50 million or more”.
On passive income it does not: “The Ontario small business limit is not subject to the federal passive income business limit reduction… eligible Ontario small businesses can receive the Ontario small business deduction regardless of the amount of passive income they earned.” A target with $150,000 of it loses the federal limit outright and keeps the Ontario one — Treadstone Law’s passive-grind page says the opposite, and CRA’s page governs. The page also notices an announced Ontario rate increase, and CRA’s rate table excludes Quebec and Alberta, which have no collection agreement with the CRA.
SECTION 08 OF 08
Both grinds look backwards: the figures setting the buyer’s first-year limit exist on closing day. Ask for the target’s Schedule 7 (Part 2 carries the adjusted aggregate investment income), Schedule 33, 34 or 35 above $10 million of taxable capital, and Schedule 23 if it has ever been associated — then the same for every corporation associated with it after closing, since C and E are group totals.
That is a price input or a contract term, not a post-closing project. A pre-closing disposition of redundant investments, or a covenant on what the vendor may do between signing and closing, moves E for the buyer’s first full year; so does whether acquisition debt sits in the target or above it, since loans to the corporation are part of its capital under s. 181.2(3).
This covers the federal deduction and the parts of section 125 a buyer of a private operating company routinely meets. Left out: specified partnership income in subsections (6) to (8), the assignment rules in (3.2), (9) and (10), farming and fishing income, and the association tests. Provisions quoted are from the consolidation current to 21 June 2026; the limit and thresholds move by budget.
No. Both reductions to the limit — the taxable capital grind and the passive investment income grind — are computed on the target’s own numbers from the preceding taxation year, and the greater of the two applies, not the sum. That means the buyer’s first-year limit is effectively fixed by the seller’s old balance sheet before the deal ever closes.
Yes, completely. A corporation must be a Canadian-controlled private corporation to claim the deduction at all, and control by non-residents or public corporations, or a listing on a designated stock exchange, ends that status at closing. Unlike the two grinds, which reduce the limit gradually, losing CCPC status removes the deduction entirely.
Not uniformly. Ontario follows the federal taxable capital grind but does not apply the federal passive income reduction provincially, so a target with $150,000 or more of passive investment income can lose its federal small business limit entirely while still keeping the Ontario small business deduction.
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