A rollover postpones gain
A startup exit may happen before its investors satisfy the Section 1202 holding period. Section 1045 provides a separate route: an eligible noncorporate taxpayer can elect to defer some or all of the gain by purchasing replacement qualified small business stock. The original stock must itself be QSBS. Reinvesting proceeds from ordinary public-company stock or another ineligible asset does not qualify.
Deferral means the gain is carried into the replacement investment through a lower tax basis. A future sale can bring that deferred gain back into the tax calculation. A later Section 1202 exclusion may be available if its requirements are met, but a rollover by itself neither guarantees that exclusion nor forgives the gain.
The two clocks to check first
- Original holding period: the stock sold must have been held for more than six months. Exactly six months does not satisfy the statutory language.
- Replacement window: qualifying stock must be purchased during the 60-day period beginning on the sale date. The sale date is part of that window.
An extension to file a tax return does not extend the statutory replacement-purchase window. Review the transaction date and eligible replacement investment before closing. A plan to invest later, a cash reserve, or a commitment without a qualifying completed stock purchase is not interchangeable with meeting the purchase requirement.
The replacement investment must meet the QSBS definition, including original issuance and the applicable company tests. Section 1045 also requires the replacement issuer's active-business requirement to be met for at least the first six months after the purchase. Ordinary income from the sale is not eligible for this deferral. Subsequent qualification for a Section 1202 exclusion involves its own continuing requirements.
Reinvesting only the profit can leave taxable gain
The calculation compares the amount realized on the sale with the cost of qualifying replacement stock, excluding costs already used for another rollover. That is different from comparing the realized gain with the replacement investment. To defer the full gain, an investor generally needs to reinvest the full amount realized.
Consider a simplified sale for $1 million of QSBS with a $100,000 basis: the realized gain is $900,000. If the investor purchases $800,000 of eligible replacement shares within the window, $200,000 of gain remains recognized and $700,000 is deferred. The replacement shares start with $800,000 of cost, reduced by the $700,000 deferred gain, leaving a $100,000 tax basis. Assume no expenses, ordinary-income component, prior use of replacement cost, or other complications.
If the investor instead purchases $1 million of qualifying replacement shares, the full $900,000 gain can be deferred under those assumptions. The replacement basis is still $100,000. The lower basis is the mechanism that preserves the deferred gain for a later tax calculation.
Holding periods can carry over, with exceptions
Section 1223(13) generally adds the original holding period to replacement property where Section 1045 produces nonrecognition. This is commonly called tacking. There are statutory exceptions, including the active-business test, and the carried-over period cannot satisfy the fresh more-than-six-month requirement for rolling over the replacement stock again.
Tacking also matters when a rollover crosses July 4, 2025. Section 1202 determines acquisition dates after applying Section 1223; a replacement purchase after that date does not automatically unlock the new three-year exclusion tiers or a fresh $15 million limit. Review the original acquisition history alongside the new rules.
The election and records are part of the transaction
The IRS reporting guidance describes reporting the sale on Form 8949 with code R and the deferred amount as an adjustment. The election generally must be made by the return due date, including extensions. Limited amended-return relief has additional conditions; it should not be treated as a routine extension.
Keep issuance evidence for both companies, acquisition and sale dates, purchase amounts, a basis schedule, and documentation of the active business. Partnership investors face additional rules governing continuous ownership, allocation limits, elections, and notices; a partner cannot assume the fund's transaction handles every personal requirement. State conformity must also be checked separately. A successful federal rollover is only one part of the exit's tax treatment.