The Securities and Exchange Commission is seeking comments on the first ever explicit “best execution” rule for municipal securities transactions proposed by the Municipal Securities Rulemaking Board. The MSRB modeled its rule on the Financial Industry Regulatory Authority’s best-execution rule for equity and non-municipal fixed income securities. Proposed MSRB Rule G-18 would generally require that, in any transaction in a municipal security for or with a customer or a customer of another dealer, a dealer must use “reasonable diligence” to ascertain the best market for the subject security and buy or sell in that market so that the resultant price to the customer is as favorable as possible under prevailing market conditions. This basic best execution obligation would not apply to transactions in municipal fund securities (such as 529 college savings plans) or to transactions with “sophisticated municipal market professionals." The MSRB intends that the proposed rule change would become effective one year after the date of SEC approval.