Nasdaq made two companion filings with the Securities and Exchange Commission to adopt a policy of attaching Aberrant Report Indicators to trade reports that Nasdaq determines to be inconsistent with the prevailing market. This policy is substantially similar to the one recently adopted by the New York Stock Exchange (NYSE), as reported in the October 17, 2008, edition of Corporate and Financial Weekly Digest. Trades that are marked by the Aberrant Report Indicator are still valid trades, i.e., they were executed and not unwound as in the case of a clearly erroneous trade. Nasdaq’s policy, like the NYSE’s, includes general numerical guidelines that will be consulted when determining whether trade prices are inconsistent with the prevailing market. The SEC approved Nasdaq’s request that the policy become effective immediately. Nasdaq also proposed that the policy be made retroactive to September 1, 2008.  

http://www.sec.gov/rules/sro/nasdaq/2008/34-59149.pdf

http://www.sec.gov/rules/sro/nasdaq/2008/34-59151.pdf