The test is written as a capability standard, and it has no scale. Rule 506(b)(2)(ii), headed "Nature of purchasers", asks about knowledge and experience in financial and business matters sufficient to evaluate the merits and risks of the prospective investment. There is no list of qualifying occupations, no examination, no asset test and no safe harbor. That is unusual in securities regulation, where thresholds are the norm, and it is why the category is used sparingly: an issuer relying on it is making a judgment it may later have to defend, about a person it may not know well.
The purchaser-representative limb is the half most summaries drop. The rule says the purchaser may meet the test "either alone or with his purchaser representative(s)", and Regulation D defines a purchaser representative separately, at 17 CFR 230.501(i). The conditions are meaningful. The representative must not be an affiliate, director, officer or employee of the issuer, or a 10 percent owner of it, subject to narrow family and common-ownership exceptions; must have knowledge and experience sufficient to evaluate the investment alone or together with the purchaser or other representatives; must be acknowledged in writing by the purchaser as their representative for that transaction; and must disclose in writing any material relationship with the issuer. So the sophistication can be borrowed, but not from the person selling the deal.
"Reasonably believes" does a great deal of work. The rule's second limb lets the condition be satisfied where "the issuer reasonably believes immediately prior to making any sale that such purchaser comes within this description". An issuer that inquires sensibly and concludes wrongly has still satisfied the rule. Compare the neighboring provision for offerings that do use general solicitation, Rule 506(c), where every purchaser must be an accredited investor and the issuer must "take reasonable steps to verify" it, with the rule listing specific documentary methods. Reasonable belief and reasonable verification are different standards, and the difference is one of the clearest signals of how the two offering routes are meant to be used.
The category is capped, which is why it stays small. Rule 506(b) permits no more than 35 purchasers who are not accredited investors, or a reasonable belief that there are no more than 35, "in offerings under this section in any 90-calendar-day period", with the counting rules set out elsewhere in Regulation D. It also forbids general solicitation and general advertising. An issuer that wants to advertise the offering must move to Rule 506(c) and take only accredited investors. So sophisticated investors are confined to a quiet, small, relationship-based corner of the private market, and an offering being promoted publicly is not one they can lawfully buy into on this basis.
What the status does not do. It is not a certification, it does not travel between deals, and no regulator issues it. It is a determination made by an issuer about one purchaser for one offering, recorded in that offering's paperwork. It also brings an obligation on the issuer's side rather than a benefit on the purchaser's: Regulation D requires an issuer selling to non-accredited purchasers to deliver specified information, which is why many issuers prefer to take accredited investors only and avoid the question entirely.
A note on why there is no number here. The SEC describes one category of exemption from registration as "private offerings to a limited number of persons or institutions", and the whole design of that category is that registration's disclosure protections are replaced by the buyer's own ability to look after themselves, whether that ability comes from wealth or from competence. The accredited investor test measures the first. This test measures the second, and putting a dollar figure on it would describe the wrong thing.