Firstly, merchant mariner credentials and medical certificates (national endorsements only) that expire in December 2018, January 2019, February 2019, March 2019, April 2019, May 2019 or June 2019, are extended as valid until July 31, 2019.
Mariners who are actively working on expired credentials that meet the expiration criteria must carry the expired credential with a copy of the attached letter.
Secondly, this extension does not change the time frame during which a credential may be renewed. A credential may be renewed at any time during its validity and for one year after expiration based on the expiration date printed on the credential.
USCG has taken another set of actions earlier this year, again due to the lapse in appropriations, in response to the partial government shutdown.