According to MSRB rules, which document does not need principal approval before being sent to a customer?

The answer provided reflects an understanding of the rules set forth by the Municipal Securities Rulemaking Board (MSRB). A preliminary official statement is intended to provide potential investors with information before the sale of municipal securities and does not require prior principal approval before distribution to customers. This facilitates timely access to relevant information for investors who may be considering a purchase, thus enhancing the transparency and efficiency of the municipal securities market.

In contrast, a final prospectus, trade confirmation, and customer account statements all necessitate principal approval prior to distribution. This requirement ensures that the information conveyed in these documents adheres to regulatory standards and is consistent with the firm's policies. By requiring principal approval for these documents, the MSRB maintains a level of oversight and compliance that further protects investors and encourages ethical practices within the industry.