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Section 1045 QSBS Rollover: Defer Gain by Reinvesting in New QSBS Within 60 Days

By The Ledgerism Editorial Team · The Ledgerism Brief Editorial Team produces original, methodology-disclosed accounting and tax research—data trackers, databases, and reference guides built to be the most-cited source in the field. Every figure is verified against primary sources including FASB, the IRS, the PCAOB, NASBA, the AICPA, and state boards of accountancy.

A Section 1045 rollover lets a holder of qualified small business stock defer gain by reinvesting the sale proceeds into new QSBS within 60 days. It is the escape hatch for shareholders who sell QSBS before clearing the five-year holding period that the Section 1202 gain exclusion demands. Done correctly, the holding period of the old stock tacks onto the new stock, keeping the path to a full exclusion alive.

What is Section 1045?

Section 1045 is the QSBS rollover provision. It permits a taxpayer who sells qualified small business stock to postpone the gain by buying replacement QSBS, in the same way Section 1031 once let real estate investors postpone gain on like-kind exchanges. The gain is not forgiven; it is rolled into the new stock by reducing the new stock’s basis, so the tax is deferred until the replacement stock is eventually sold without another rollover.

The provision matters because Section 1202, the headline gain exclusion for QSBS, generally requires a five-year holding period before the exclusion applies. A shareholder forced to sell at year three, whether because of an acquisition, a liquidity need, or a co-founder dispute, would normally lose the exclusion entirely. Section 1045 bridges that gap. By rolling proceeds into new QSBS and tacking the holding period, the shareholder can keep building toward the five-year mark and the eventual Section 1202 exclusion.

The stock sold and the stock bought must both meet the QSBS definition of Section 1202(c): stock of a domestic C corporation with aggregate gross assets of $50 million or less at issuance, acquired at original issue, with the corporation meeting the active business requirement. Section 1045 borrows the Section 1202 definition wholesale, so the two provisions live in the same technical universe.

Who qualifies for a Section 1045 rollover

Three groups of conditions govern eligibility: the seller, the stock sold, and the replacement stock.

The seller

Any taxpayer other than a C corporation can elect Section 1045. That includes individuals, partnerships, S corporations, trusts, and estates. When a pass-through entity sells QSBS and rolls the proceeds, the rollover can be made either at the entity level or, in some cases, at the partner level, under the detailed rules of Treas. Reg. 1.1045-1. The taxpayer must have held the sold QSBS for more than six months at the time of sale (Section 1045(a)).

The stock sold

The stock disposed of must be QSBS as defined in Section 1202(c), held more than six months. Note the contrast with Section 1202 itself, which requires more than five years. Section 1045 deliberately uses the shorter six-month floor so that early sellers retain a route to deferral.

The replacement stock

The taxpayer must purchase replacement QSBS during the 60-day period beginning on the date of the sale (Section 1045(a)(2)). The replacement stock must itself satisfy the QSBS requirements of Section 1202(c), including the active business requirement, during substantially all of the taxpayer’s holding period. The replacement company must meet the active business requirement for the six months after purchase under Section 1045(b)(4)(B), a wrinkle that can trip up rollovers into a company that is still pre-revenue.

How Section 1045 works (mechanics)

The rollover runs through a sequence of computations.

Step 1: Compute the realized gain

Start with the amount realized on the sale of the original QSBS less its adjusted basis. This is the gross gain potentially eligible for deferral.

Step 2: Compare proceeds to reinvestment

Gain is recognized only to the extent the amount realized on the sale exceeds the cost of the replacement QSBS purchased within 60 days (Section 1045(a)). If the taxpayer reinvests the entire proceeds, no gain is currently recognized. If the taxpayer reinvests only part, gain is recognized to the extent of the unreinvested proceeds.

Step 3: Reduce the basis of replacement stock

The deferred gain reduces the basis of the replacement QSBS under Section 1045(b)(3). This is what makes the deferral temporary: when the replacement stock is later sold without a further rollover, the lower basis produces a larger gain that captures the previously deferred amount.

Step 4: Tack the holding period

For purposes of the five-year holding period under Section 1202, the holding period of the original QSBS is added to the holding period of the replacement QSBS (Section 1045(b)(4)). A shareholder who held the first stock three years and the replacement two years has a combined five-year holding period and can claim the Section 1202 exclusion on the eventual sale, subject to the other Section 1202 limits.

Step 5: Make the election

The election is made on a timely filed return, including extensions, for the year of the sale. Per Rev. Proc. 98-48, the taxpayer reports the entire gain on Schedule D and Form 8949, then enters a Section 1045 adjustment to back out the deferred portion, and attaches a statement describing the sold and replacement QSBS. The election is generally irrevocable once made.

Step 6: Track the deferred gain across the chain

Because the deferred gain reduces the basis of the replacement stock, the taxpayer carries a built-in gain into every successive position. A founder who chains three rollovers ends up holding stock with a basis far below its cost, and the full deferred amount surfaces the moment the chain breaks with a sale that is not rolled over and does not qualify for exclusion. Good records matter here as much as the election itself, because the IRS and a future acquirer’s diligence team will both want to trace the basis from the original QSBS through each replacement. Where the chain eventually lands in stock that clears the five-year holding period and meets the other Section 1202 tests, the deferred gain can be excluded, but the burden is on the taxpayer to show the unbroken lineage of qualifying stock.

Partnership-level versus partner-level rollovers

When a partnership holds QSBS and sells it, Treas. Reg. 1.1045-1 gives two paths. The partnership itself can buy replacement QSBS within 60 days and make the election at the entity level, in which case the deferral flows to the partners who held interests at the time of sale. Alternatively, the partnership can distribute the proceeds and each eligible partner can buy replacement QSBS individually and elect at the partner level. The partner-level path is useful when partners disagree about reinvesting, but it requires each partner to independently meet the 60-day window and the QSBS requirements on their own replacement stock. Mismatched elections across partners are a common source of error, so the partnership agreement should address how a QSBS sale will be handled before the sale closes.

Section 1045 rules and limits

The table below collects the key parameters that govern a rollover.

The six-month replacement active business test

A point that surprises many founders is the requirement in Section 1045(b)(4)(B) that the replacement corporation meet the active business requirement of Section 1202 for the six months following the purchase. Rolling proceeds into a company that has not yet begun active operations, or that is still primarily holding cash from a recent financing round, can fail this test even though the company is plainly a startup. The active business requirement looks at whether at least 80 percent of the corporation’s assets are used in the active conduct of a qualified trade or business, and a pre-revenue shell sitting on a large cash balance may not clear that bar in its first six months. Founders evaluating a rollover target should confirm the company is actually deploying its capital into operations, not just holding it.

Worked example

A founder acquired QSBS at original issue for $200,000. Three years later, the company is acquired and the founder receives $1,200,000, a realized gain of $1,000,000. Because the stock was held only three years, it does not qualify for the Section 1202 exclusion on its own. The founder wants to defer the gain and keep building toward the five-year mark.

Within 60 days of the sale, the founder reinvests the full $1,200,000 of proceeds into newly issued QSBS of another qualifying startup. Under Section 1045(a), because all proceeds were reinvested, none of the $1,000,000 gain is currently recognized. Under Section 1045(b)(3), the basis of the new $1,200,000 of QSBS is reduced by the $1,000,000 deferred gain to $200,000. Under Section 1045(b)(4), the founder’s three-year holding period in the original stock tacks onto the new stock.

Two years later, the founder has held the replacement QSBS for two years, which combined with the tacked three years gives a five-year holding period. If the founder sells the replacement stock at that point and the Section 1202 requirements are met, the previously deferred gain can fall within the Section 1202 exclusion, potentially eliminating tax on up to the greater of $10 million or, under the post-OBBBA rules, the increased per-issuer cap times the qualifying basis. The rollover converted a stranded three-year position into a path to full exclusion.

Recent changes (OBBBA and TCJA)

The mechanics of Section 1045 were not directly amended by the Tax Cuts and Jobs Act of 2017 or by the One Big Beautiful Bill Act signed July 4, 2025. The 60-day window, the basis reduction, and the holding-period tacking all remain as enacted. What changed is the payoff at the end of the chain. The OBBBA expanded Section 1202 for QSBS acquired after the enactment date, raising the per-issuer gain exclusion cap above the prior $10 million floor and introducing tiered exclusion percentages tied to the holding period.

Because Section 1045 feeds the Section 1202 exclusion through holding-period tacking, the richer Section 1202 makes a successful rollover more valuable than before. A founder who rolls pre-enactment QSBS into post-enactment QSBS must be careful, though, because the replacement stock’s own acquisition date controls which version of the Section 1202 cap applies to it. Practitioners are watching for Treasury guidance on how the tacking rule interacts with the new tiered exclusion, since the statute tacks the holding period but does not automatically tack the acquisition-date character that sets the cap.

Common pitfalls

• Missing the 60-day reinvestment window. The window runs from the date of sale and is strict; there is no reasonable-cause extension in the statute (Section 1045(a)(2)).
• Reinvesting in stock that is not QSBS. The replacement must independently meet the Section 1202(c) definition, including the C corporation requirement and the $50 million gross assets test at issuance.
• Forgetting the basis reduction. The deferred gain reduces replacement basis under Section 1045(b)(3); ignoring it understates gain on the eventual sale and creates an exposure on audit.
• Selling stock held six months or less. The sold stock must be held more than six months; a quick flip does not qualify for rollover (Section 1045(a)).
• Replacement company failing the active business test. The replacement corporation must meet the active business requirement for the six months after purchase under Section 1045(b)(4)(B), which a pre-operating shell may fail.
• Missing the election statement. The deferral requires the election under Rev. Proc. 98-48, including the attached statement; reporting the net gain without the election can invalidate the rollover.
• Assuming corporate sellers qualify. C corporations cannot elect Section 1045; the provision is limited to non-corporate taxpayers and pass-throughs.

Frequently asked questions

How is Section 1045 different from Section 1202?

Section 1202 excludes QSBS gain after a five-year hold. Section 1045 defers gain when the stock is sold before five years by rolling proceeds into new QSBS within 60 days. Section 1045 is the bridge that keeps the Section 1202 exclusion reachable.

Do I have to reinvest all the proceeds?

No, but gain is recognized to the extent proceeds are not reinvested. Reinvesting the full amount realized defers the entire gain; reinvesting part defers only the corresponding part.

Does the holding period really carry over to the new stock?

Yes. Section 1045(b)(4) tacks the holding period of the sold QSBS onto the replacement QSBS for purposes of the Section 1202 five-year test, which is the central benefit of the rollover.

Can a partnership use Section 1045?

Yes. Partnerships and S corporations can roll over QSBS gain, and Treas. Reg. 1.1045-1 sets out detailed rules for whether the election is made at the entity or partner level and how it flows to eligible partners.

When is the election due?

The election is made on the timely filed return, including extensions, for the year of the sale, following Rev. Proc. 98-48. Once made, it is generally irrevocable.

What is the minimum holding period for the sold stock?

More than six months under Section 1045(a). This is far shorter than the five years Section 1202 requires for outright exclusion, which is the point of the provision.

Can I roll over more than once?

Yes. A taxpayer can chain multiple rollovers, each time deferring gain and tacking holding periods, until eventually selling without a rollover or qualifying for the Section 1202 exclusion. Compare this to a Section 1244 loss, which addresses the opposite outcome when the investment fails.

What happens if the replacement company later loses QSBS status?

If the replacement corporation fails the QSBS requirements during the holding period, the deferred gain may become recognizable and the eventual Section 1202 exclusion may be lost. The active business requirement must be monitored after the rollover.