17 C.F.R. § 230.159
Information available to purchaser at time of contract of sale
(a) For purposes of section 12(a)(2) of the Act only, and without affecting any other rights a purchaser may have, for purposes of determining whether a prospectus or oral statement included an untrue statement of a material fact or omitted to state a material fact necessary in order to make the statements, in the light of the circumstances under which they were made, not misleading at the time of sale (including, without limitation, a contract of sale), any information conveyed to the purchaser only after such time of sale (including such contract of sale) will not be taken into account.
(b) For purposes of section 17(a)(2) of the Act only, and without affecting any other rights the Commission may have to enforce that section, for purposes of determining whether a statement includes or represents any untrue statement of a material fact or any omission to state a material fact necessary in order to make the statements made, in light of the circumstances under which they were made, not misleading at the time of sale (including, without limitation, a contract of sale), any information conveyed to the purchaser only after such time of sale (including such contract of sale) will not be taken into account.
(c) For purposes of section 12(a)(2) of the Act only, knowing of such untruth or omission in respect of a sale (including, without limitation, a contract of sale), means knowing at the time of such sale (including such contract of sale).