Constructive Ownership of Stock (§ 318)

IRC § 318 is the attribution engine of the corporate tax code — a set of rules that deem a taxpayer to own stock held by related parties, so that attempts to circumvent ownership percentage thresholds by distributing stock among family members or controlled entities do not succeed. When the tax law asks "what percentage of this corporation does this person own?", § 318 requires you to add not just shares held directly but also shares owned by the taxpayer's spouse, children, grandchildren, and parents, shares proportionately owned through partnerships, estates, trusts, and corporations, and shares the taxpayer has an option to acquire — a far broader universe than actual registered ownership. The provision applies wherever the Code incorporates it by reference: § 302 (stock redemptions), § 304 (related-party redemptions), § 351 (tax-free contributions), § 355 (spin-offs), § 856 (REIT rules), § 1504 (affiliated group definitions), and many others. Failing to run a § 318 analysis before advising on a redemption, spin-off, or ownership threshold determination is one of the most common errors in closely-held business tax practice — a shareholder who appears to have completely terminated her interest in a family corporation may, through § 318 attribution from her children's shares, be deemed to still own a significant stake.

Current Law (2026)

Legal Authority

• 26 U.S.C. § 318(a)(1) — Family attribution: individual deemed to own stock of spouse, children, grandchildren, and parents; does not include siblings, cousins, in-laws, or other relatives
• 26 U.S.C. § 318(a)(2) — Attribution from entity to beneficiary/owner: (A) partnership — each partner deemed to own proportionate share of partnership's stock; (B) estate — each beneficiary deemed to own proportionate share of estate's stock; (C) trust — each beneficiary deemed to own proportionate share of trust's stock proportional to their actuarial interest; (D) corporation — each shareholder owning 50%+ by value deemed to own proportionate share of corporation's stock
• 26 U.S.C. § 318(a)(3) — Attribution to entity from owner/beneficiary: (A) partnership deemed to own stock of any partner; (B) estate deemed to own stock of any beneficiary; (C) trust deemed to own stock of any beneficiary; (D) corporation deemed to own stock of any 50%+ shareholder
• 26 U.S.C. § 318(a)(4) — Option attribution: person who holds an option to purchase stock is deemed to own that stock for § 318 purposes
• 26 U.S.C. § 318(a)(5) — Operating rules: rules for chaining attribution; stock attributed to a person via family rules cannot be reattributed to another family member through family rules (but may be reattributed through entity rules); entity-to-owner attribution can be chained through another entity
• 26 U.S.C. § 318 (DB) — Constructive ownership of stock: an S corporation and its shareholders are treated like a partnership and partners for attribution purposes; a beneficiary's "remote contingent" trust interest is ignored if it is 5% or less by actuarial value; these attribution rules apply to stock redemptions (§ 302), related-corporation redemptions (§ 304), controlled foreign corporation rules, and certain foreign-corporation reporting requirements; a legally adopted child counts the same as a biological child for family attribution; tax-exempt employee retirement trusts under § 401(a)/501(a) are excluded from trust attribution

Key Mechanics

Section 318 constructive ownership works through four attribution categories that operate independently and cumulatively: (1) family attribution — shares owned by spouse, children, grandchildren, and parents are attributed to the taxpayer (but not siblings); (2) entity-to-beneficiary attribution — a beneficiary of a trust, partner in a partnership, or shareholder of a corporation is treated as owning the entity's shares proportionally; (3) beneficiary-to-entity attribution — shares owned by a partner or beneficiary are attributed to the entity; and (4) option attribution — an option to acquire stock is treated as actual ownership. These rules chain: if A owns 50% of a corporation that owns 80% of target stock, A constructively owns 40% of the target (50% × 80%). The constructive ownership result determines whether a stock redemption qualifies as a sale (capital gain) under § 302 or is treated as a dividend — the central tax stakes of the § 318 analysis.

How It Works

Section 318 creates a map of "who owns what" that is radically different from who the registered shareholder is. The four attribution categories operate independently and cumulatively — a taxpayer's constructive ownership includes shares attributed from any combination of sources.

Family attribution (§ 318(a)(1)) is the most important and most frequently encountered category. An individual is deemed to own stock held by their spouse, children, grandchildren, and parents — but not siblings, cousins, in-laws, nieces, nephews, or more distant relatives. The omission of siblings is significant and sometimes counterintuitive: two brothers each owning 50% of a corporation are not considered to own each other's shares under § 318. The inclusion of grandchildren (but not other collateral relatives) reflects the statutory design around the lineal family line. Family attribution is one-directional in some senses: a parent is deemed to own the child's shares, and the child is deemed to own the parent's shares, but stock attributed to a person via family attribution cannot be reattributed through the family rules to yet another person (§ 318(a)(5)(B)).

Entity-to-beneficiary attribution (downward, § 318(a)(2)) attributes the entity's stock holdings proportionately to its owners. A 30% partner in a partnership is deemed to own 30% of any stock the partnership owns. A trust beneficiary with a 40% actuarial interest is deemed to own 40% of the trust's stock. A shareholder who owns 60% of a holding company is deemed to own 60% of any stock that holding company owns. There is no ownership threshold for downward attribution from partnerships, estates, and trusts — even a 1% partner is attributed their proportionate share of partnership stock. For corporations, the downward attribution only applies to shareholders owning 50% or more by value.

Beneficiary-to-entity attribution (upward, § 318(a)(3)) attributes a person's stock holdings to the entity in which they have an interest. A partnership is deemed to own all stock of any partner. An estate or trust is deemed to own all stock of any beneficiary. A corporation is deemed to own all stock of any 50%+ shareholder. Upward attribution from partnerships, estates, and trusts is unlimited — if you own 1% of a partnership and also own 100 shares of XYZ Corp, the partnership is deemed to own those 100 shares of XYZ Corp regardless of your small ownership stake.

Option attribution (§ 318(a)(4)) treats the holder of an option, warrant, or convertible instrument as the owner of the underlying stock. This prevents the obvious workaround of substituting an option for actual stock to avoid ownership thresholds. If you hold options on 100,000 shares of a corporation, you are deemed to own all 100,000 shares for § 318 purposes regardless of whether the options are currently exercisable.

Chaining is the most complex aspect of § 318. The rules permit some combinations of attribution while blocking others. The key anti-chaining rule is that stock attributed to an individual through the family rules cannot be further attributed from that individual to their family members through the family rules — preventing unlimited "daisy chain" attribution. However, stock can be attributed from an entity to an individual (entity-to-owner), and then from that individual to another entity (owner-to-entity) — this chain is allowed. In practice, tax advisors must trace the complete attribution chain for each taxpayer and each entity in the family structure to determine constructive ownership.

The complete termination waiver under § 302(c)(2) is the most commonly used relief from § 318 in practice. When a shareholder wants to completely terminate their interest in a closely held corporation through a redemption, family attribution from their relatives' stock may prevent the § 302(b)(3) complete termination test from being satisfied. Section 302(c) allows the shareholder to waive family attribution if: (1) the shareholder retains no interest in the corporation for 10 years other than as a creditor (no employment, consulting, officer role, or director position), (2) the shareholder does not reacquire any stock for 10 years, and (3) the shareholder files a waiver agreement with the IRS on their tax return for the year of the redemption. Violation of the 10-year conditions retroactively eliminates the waiver and causes the redemption to be recharacterized as a dividend.

How It Affects You

If you're a shareholder in a family business planning a buyout: Before you assume your buyout qualifies as a complete termination of your interest for tax purposes, run the § 318 analysis. Start by listing every family member who holds stock — your spouse, children, grandchildren, and parents. Any shares they own are attributed to you. If your children collectively own 100% of the company after you sell, you are constructively deemed to still own 100% through attribution — and your "buyout" is treated as a dividend rather than a capital gain. To escape this result, you need the § 302(c) family attribution waiver, which requires genuinely severing all ties with the company for 10 years. If you can't commit to a full 10-year hands-off period, restructure the transaction or accept dividend treatment.

If you're a tax advisor on any transaction with ownership percentage thresholds: § 318 analysis is mandatory before advising on any transaction where a percentage of ownership matters — § 302 redemptions, § 304 related-party redemptions, § 355 spin-offs, REIT qualification tests, affiliated group determinations. The analysis must be fresh (ownership changes when stock is redeemed, transferred, or options are granted) and must cover all four attribution categories. Missing entity-to-owner attribution (where a family LLC or trust holds shares) is a common error — the entity's stock is attributed to its owners regardless of whether those owners think of themselves as shareholders in the target corporation.

If you're structuring a spin-off (§ 355): Section 355 spin-offs require careful § 318 analysis to ensure the post-spin-off ownership structure doesn't violate the device and active business requirements. The § 318 rules determine what counts as a "5% shareholder" for certain § 355 safe harbors and who is "related" for purposes of restrictions on post-spin transfers. Attribution from family members to related entities (and vice versa) can create relatedness that triggers the § 355 anti-abuse rules.

If you hold warrants or convertible instruments in a startup or public company: For any corporate tax analysis where your ownership percentage matters — stock redemptions, REIT qualification, affiliated group rules — your warrants and convertibles count as stock under § 318(a)(4). This can push you over a 50% threshold even if your directly held shares represent a smaller position. In private markets where investors hold combinations of preferred stock, warrants, and convertibles, the § 318 constructive ownership analysis can be substantially different from the cap table equity percentages.

State Variations

Section 318 is a federal provision that applies to federal corporate income tax determinations. States with corporate income taxes generally follow the federal § 318 attribution rules when applying analogous state-law ownership thresholds, but state-specific rules vary. The § 318 attribution rules don't have direct state equivalents in most states' individual income tax codes — they arise primarily in corporate and business entity contexts.

Implementing Regulations

• 26 CFR 1.318-1 — Constructive ownership of stock; general principles; the four attribution categories
• 26 CFR 1.318-2 — Specific attribution rules; application of family attribution; entity-to-owner and owner-to-entity rules
• 26 CFR 1.318-3 — Estates, trusts, and partnerships as constructive owners; attribution to and from these entities
• 26 CFR 1.318-4 — Constructive ownership as actual ownership; when attributed stock is treated as actually owned for applying further attribution rules; chaining rules
• 26 CFR 1.302-4(b) — The § 302(c)(2) family attribution waiver; requirements and mechanics

Pending Legislation

No legislation to reform § 318 is pending as of 2026. The sibling attribution gap — brothers and sisters are not included in family attribution, which can create planning opportunities in sibling-owned businesses — has been noted in academic literature but is not currently targeted for legislative change. Comprehensive business tax reform proposals that address closely-held corporations may implicitly touch § 318 attribution rules.

Recent Developments

• Private equity and attribution complexity: The growth of private equity fund structures with complex investor networks has created § 318 analysis challenges. A PE fund's portfolio companies may be related to each other through the fund's ownership, triggering § 318 upward attribution from portfolio company shareholders (the fund) to the fund itself. Tax advisors to PE firms must map § 318 attribution across the entire fund portfolio when advising on redemptions, spin-offs, or REIT elections.
• Family trust planning and attribution: The use of grantor retained annuity trusts (GRATs), spousal lifetime access trusts (SLATs), and other irrevocable trusts in estate planning creates § 318 attribution questions. A trust beneficiary is attributed the trust's stock proportionate to their actuarial interest — meaning a child who is the primary beneficiary of a trust holding company stock is deemed to own a significant portion of that stock, which can affect the child's constructive ownership percentage in any company the trust holds.
• REIT qualification and attribution: REITs must comply with both a "5/50 test" (no five persons can own more than 50% of the REIT's shares in the last half of the taxable year) and concentration limits. The § 318 attribution rules determine who counts as a "person" for this purpose — family attribution and entity attribution can cause seemingly dispersed ownership to be concentrated for REIT qualification purposes. REIT sponsors apply § 318 analysis at inception and on an ongoing basis as ownership changes.
• Employee stock options and § 318: Options granted to employees and directors under equity compensation plans are attributed to the optionee under § 318(a)(4). For closely-held corporations with significant employee option plans, this can cause employees with large option grants to be constructively treated as more-than-50% shareholders — triggering related-party treatment under various Code provisions (including § 267 loss disallowance and § 302 redemption rules) even though the options have not been exercised and the employees don't think of themselves as majority owners.