Section 1045 rollover is the IRS provision letting QSBS holders defer capital gains by rolling sale proceeds into new QSBS within 60 days. It applies to QSBS sold before the 5-year §1202 holding period, preserving the original holding period (basis tacks to the new investment) and giving the holder another chance to reach the 5-year mark. Section 1045 mechanics themselves are unchanged by the One Big Beautiful Bill Act, but OBBBA's tiered exclusion (50% at 3 years, 75% at 4, 100% at 5) means a Section 1045 rollover can start producing partial Section 1202 benefit at 3 years rather than the old all-or-nothing 5-year cliff. Important nuance: the exclusion-percentage regime that applies on eventual sale of replacement sto...