Section 1045 QSBS Rollover Playbook
A founder sells shares and books a large gain. Section 1045 lets a taxpayer who sells qualified small business stock (QSBS) defer the gain by buying other QSBS within 60 days. It is a rollover, not an exclusion: the tax is postponed, the deferred gain cuts the replacement stock's basis, and the bill arrives later.
This playbook covers the statute in 26 U.S.C. § 1045, the partnership rules in Regulation § 1.1045-1, and the Schedule D filing mechanics — with the § 1202 exclusion itself in the QSBS master guide.
Founder & CEO Insight — Enow A. Jovial
The five gates
Section 1045(a) provides: "In the case of any sale of qualified small business stock held by a taxpayer other than a corporation for more than 6 months and with respect to which such taxpayer elects the application of this section, gain from such sale shall be recognized only to the extent that the amount realized on such sale exceeds — (1) the cost of any qualified small business stock purchased by the taxpayer during the 60-day period beginning on the date of such sale, reduced by (2) any portion of such cost previously taken into account under this section."
| Gate | What it requires | Authority |
|---|---|---|
| Seller | A taxpayer other than a corporation — an individual, a trust, or an estate. | 26 U.S.C. § 1045(a) |
| Stock | C corporation stock acquired at original issue for money, property other than stock, or services. | 26 U.S.C. §§ 1045(b)(1), 1202(c) |
| Holding period | More than 6 months before the sale, measured without regard to § 1223 — no tacking from a gift or inheritance. | 26 U.S.C. §§ 1045(a), 1045(b)(4)(A) |
| Reinvestment | Other QSBS purchased during the 60-day period beginning on the date of the sale. | 26 U.S.C. § 1045(a)(1) |
| Election | The taxpayer elects on the return for the year of sale, by the due date with extensions. | 26 U.S.C. § 1045(a); Schedule D instructions |
The 6-month test is short on purpose — 6 months, not the 3 or 5 years § 1202 needs.
The two formulas
Two formulas decide the outcome: the gain taxed now, and the basis of the replacement stock.
Recognized gain can never be less than zero: if the replacement stock costs more than the amount realized, the whole gain is deferred. Under § 1045(b)(3) the deferred gain reduces the replacement stock's basis "in the order acquired." And § 1045(a) does not apply to gain treated as ordinary income.
Worked example 1: the full rollover
Example: Maya buys 10,000 shares of QSBS at original issue on August 1, 2025, for $200,000, and sells on Monday, March 2, 2026, for $500,000. She held the stock 213 days, so the more-than-6-months test is met. On Monday, April 20, 2026, she buys replacement QSBS in a second startup for $500,000 and elects § 1045 on her 2026 return.
Maya pays no tax on the $300,000 — $60,000 deferred at a stated 20 percent rate, $71,400 if the 3.8 percent net investment income tax also applies. Her replacement stock carries a $200,000 basis though she paid $500,000 for it, so the $300,000 will be taxed when she sells it, unless § 1202 erases it first. The window ran March 3 through Friday, May 1, 2026; her April 20 purchase landed on day 49.
Worked example 2: the partial rollover
Example: Daniel sells QSBS for $400,000 against a $150,000 basis and buys replacement QSBS for $350,000 inside the window. The shortfall is taxed now; the rest is deferred.
Daniel owes $10,000 on the $50,000, defers $200,000, and carries a $150,000 basis in stock he paid $350,000 for.
Model the tax on any recognized gain with the tax estimator before you file.
Worked example 3: two ways to lose it
Example: Priya sells QSBS on Monday, March 2, 2026, for $500,000 against a $200,000 basis — a $300,000 gain. She buys replacement QSBS on Saturday, May 2, 2026, for $500,000 — one day after the 60-day period ended Friday, May 1. The rollover fails entirely: the full $300,000 is recognized in 2026, tax of $60,000 at a stated 20 percent rate, and the replacement stock keeps its full $500,000 cost basis because no gain was deferred.
Suppose Priya had bought her original shares on Wednesday, October 15, 2025, and sold them on Monday, March 16, 2026 — 152 days, 5 months and 1 day. She held the stock for less than 6 months, so § 1045(a) never applies, however fast she reinvests, and tacking under § 1223 does not help.
Partnerships and pass-throughs
A partnership that holds QSBS for more than 6 months, sells it, and buys replacement QSBS can elect under § 1045 at the entity level, and an eligible partner can elect individually. Regulation § 1.1045-1 governs: each partner's share of the deferred gain follows the partner's share of the gain, and the partnership's replacement-stock basis is reduced partner by partner. An eligible partner may opt out — by recognizing the gain, or by electing at partner level instead — and a partner who must recognize gain must notify the partnership in writing.
Example: PRS, a partnership, sells QSB stock for $1,500,000 and realizes a $750,000 gain. Partner A holds a 50 percent interest, so A's share is $750,000 of the amount realized and $375,000 of the gain. A buys replacement QSB stock directly for $750,000 within 60 days of the sale and elects § 1045.
A defers the full $375,000. If the partnership itself buys the replacement stock and elects, the deferral flows to every eligible partner and the partnership must notify all partners and state each share. The Schedule D instructions add the holding condition: the benefit applies only if the partner held the interest for the entire period the entity held the QSB stock. Partners find the numbers on Schedule K-1 (Form 1065), box 11.
Stacking the rollover onto the § 1202 exclusion
The real payoff is combining the rollover with § 1202: the replacement stock is itself QSBS, so it starts its own clock toward the exclusion. For stock acquired after the applicable date — July 4, 2025, P.L. 119-21's enactment date — § 1202(a)(5) sets a tiered exclusion: 50 percent at 3 years, 75 percent at 4 years, 100 percent at 5 years or more. Stock acquired on or before that date keeps the older rule: 50 percent, or 100 percent if acquired after September 27, 2010 and held more than 5 years.
Example: take Maya's replacement stock, bought Monday, April 20, 2026, for $500,000, with a $200,000 basis after the § 1045(b)(3) reduction, sold Thursday, May 15, 2031, for $1,100,000 — held 5 years and 25 days, past the 5-year tier.
The cap check under § 1202(b) passes: the per-issuer limit is the greater of $15,000,000 or 10 times the adjusted basis of the stock disposed of — 10 × $200,000 = $2,000,000 — so the limit is $15,000,000, and the $900,000 exclusion sits well inside it. Maya's $900,000 of gain is never taxed: § 1045 moves it into new stock, and § 1202 erases it if the new stock is held long enough.
Selling early costs: had Maya sold the same stock on Wednesday, April 25, 2029, for $800,000 — held 3 years and 5 days — her gain would be $600,000, the 50 percent exclusion would shelter $300,000, and the rest would be taxable as 28-percent rate gain, for $84,000 of tax.
Rollover, exclusion, § 1031, or QOF?
Four deferral tools; the choice turns on three questions: what was sold, how fast the money must move, and whether the gain should disappear or merely wait.
| Route | What it defers | Reinvestment window | What the gain becomes | Authority |
|---|---|---|---|---|
| § 1045 rollover | Gain from QSBS held >6 months; non-corporate seller | 60 days from sale | Deferred; basis cut; excludable later | 26 U.S.C. § 1045(a) |
| § 1202 exclusion alone | Gain from QSBS held ≥3 years (post-2025 stock) | None — hold, then sell | Excluded 50/75/100% by tier | 26 U.S.C. § 1202(a)(1), (a)(5) |
| § 1031 exchange | Gain from real property held for business/investment | 45 days to identify, 180 days to close | Deferred; basis carried over | Section 1031 playbook |
| QOF investment | Almost any capital gain | 180 days from realization | Deferred; 10-year hold can exclude new gain | QOF playbook |
The rollover wins when the asset is QSBS, the seller is an individual or trust, and the next investment is another startup the seller wants. It loses when the seller wants public stock, real estate, or a fund — none of those is QSBS — or held the original stock less than 6 months.
Filing the election
The election is made on the return, not by a separate form, and the Schedule D instructions give the procedure.
- Report the sale on Form 8949, Part I or Part II depending on the holding period, exactly as if no election were being made — proceeds in column (d), basis in column (e).
- Enter "R" in column (f) — the rollover marker; the exclusion uses "Q" instead, so the two codes must never be mixed on one line.
- Enter the postponed gain as a negative number in column (g), in parentheses, so column (h) shows only the recognized gain.
- Complete the remaining columns and carry the Form 8949 totals to Schedule D.
- Elect by the due date, including extensions, of the return for the year of sale. For a 2026 sale, an individual return is due Thursday, April 15, 2027, or Friday, October 15, 2027 with an extension.
- If the original return was filed on time, the election can still be made on an amended return filed no later than 6 months after the due date excluding extensions — by October 15, 2027 for a 2026 sale — headed "Filed pursuant to section 301.9100-2".
- Keep the paper trail: the sale confirmation, the replacement purchase confirmation, the issuer's QSBS status letter, and the basis computation. A partnership adjusting replacement-stock basis must attach a statement setting out the computation and the amount allocated to each partner.
Most rollovers quietly break here: an individual reports the sale under the taxpayer's own Social Security Number on Form 1040; an estate or trust reports under its Employer Identification Number on Form 1041. A pass-through entity reports the sale on its own return — a partnership on Form 1065 with the § 1045 gain stated on Schedule K-1, box 11, and an S corporation on Form 1120-S. A CPA reviewing the file checks that the seller is not a C corporation, that the replacement issuer is a C corporation with aggregate gross assets under $75,000,000, and that the K-1, Form 8949, and Schedule D agree.
Failure modes
The most common is the calendar: a founder who negotiates the replacement purchase for 61 days instead of 60, or who signs inside the window but closes outside it — the statute counts the purchase, not the signature. The second is the issuer: a startup that converted from an LLC to a C corporation after the founder bought in, or that crossed the $75,000,000 gross-assets ceiling before issuance, is not a qualified small business. The third is the double count: replacement stock already used to shelter one sale cannot shelter a second. The fourth is the entity: a C corporation that sells QSBS cannot elect at all, and the holding structure has to be fixed before the sale. The fifth is revocation: a § 1045 election is revocable only with the Commissioner's prior written consent, obtained by private letter ruling under Regulation § 1.1045-1(a).