On January 23, 2013, the Securities and Exchange Commission (SEC) amended Exchange Act Rule 17Ad-17 to implement the requirements of Section 929W of the Dodd-Frank Wall Street Reform and Consumer Protection Act. The amendments add a requirement that "paying agents" send a one-time notification to "unresponsive payees" stating that the agent has sent a securityholder a check that has not yet been negotiated.
The effective date for the amendments is January 23, 2014. Therefore, the first potential notice to unresponsive payees would be due no later than August 23, 2014.
See the The Gold Book for more information.