46 CFR 10.205: Validity and term of merchant mariner credentials
Last reviewed: October 14, 2026
This section sets the validity rules for a Merchant Mariner Credential (MMC). An MMC is valid for 5 years from issuance, and a mariner may not serve under one past its expiration date. It also covers renewal timing, replacement of older credentials, and the capacities an endorsement authorizes.
What it says
An MMC is valid for a term of 5 years from the date of issuance.
46 CFR 10.205(a)“An MMC is valid for a term of 5 years from the date of issuance.”
Unless the applicant asks in writing for immediate issuance, the Coast Guard will post-date the issuance of an MMC renewal that includes no other transactions by up to 8 months from the date it accepts a complete application.
46 CFR 10.205(a)“Except upon the written request for the immediate issuance by the applicant, the Coast Guard will post-date the issuance of an MMC renewal that includes no other transactions up to 8 months”
All endorsements are valid until the expiration date of the MMC on which they appear, unless otherwise noted.
46 CFR 10.205(b)“All endorsements, unless otherwise noted, are valid until the expiration date of the MMC on which they appear.”
A mariner may not serve under the authority of an MMC past its expiration date.
46 CFR 10.205(c)“A mariner may not serve under the authority of an MMC past its expiration date.”
An expired MMC may be renewed during an administrative grace period of up to 1 year beyond its expiration date, as provided in § 10.227(h) of this part.
46 CFR 10.205(c)“An expired MMC may be renewed during an administrative grace period of up to 1 year beyond its expiration date as per § 10.227(h) of this part.”
When an MMC is renewed or re-issued before its expiration date in accordance with § 10.227, the MMC that has been replaced becomes invalid, unless paragraph (a) of this section says otherwise.
46 CFR 10.205(d)“the MMC that has been replaced becomes invalid unless otherwise noted in paragraph (a) of this section.”
An MMC is not valid until both the applicant and a duly authorized Coast Guard official have signed it.
46 CFR 10.205(e)“An MMC is not valid until signed by the applicant and a duly authorized Coast Guard official.”
A mariner's endorsements authorize service in any endorsed capacity, in any lower capacity in the same department, or in any capacity covered by a general endorsement on the MMC.
46 CFR 10.205(f)“A mariner's endorsements authorize the holder to serve in any capacity endorsed on the MMC, or in any lower capacity in the same department, or in any capacity covered by a general endorsement thereon.”
Common questions
How long is a Merchant Mariner Credential valid?
An MMC is valid for a term of 5 years from the date of issuance.
“An MMC is valid for a term of 5 years from the date of issuance.”
Can I work on an expired MMC?
No. A mariner may not serve under the authority of an MMC past its expiration date, but an expired MMC may be renewed during an administrative grace period of up to 1 year beyond expiration.
“A mariner may not serve under the authority of an MMC past its expiration date.”
Is an MMC valid before it is signed?
No. An MMC is not valid until the applicant and a duly authorized Coast Guard official have signed it.
“An MMC is not valid until signed by the applicant and a duly authorized Coast Guard official.”
What happens to my old credential when I renew my MMC?
When an MMC is renewed or re-issued before its expiration date under § 10.227, the replaced MMC becomes invalid, unless paragraph (a) says otherwise.
“the MMC that has been replaced becomes invalid unless otherwise noted in paragraph (a) of this section.”
The text of 46 CFR 10.205
Electronic Code of Federal Regulations (eCFR), current as of March 31, 2026 · Read it on eCFR
Validity of a Merchant Mariner Credential
(a) An MMC is valid for a term of 5 years from the date of issuance. Except upon the written request for the immediate issuance by the applicant, the Coast Guard will post-date the issuance of an MMC renewal that includes no other transactions up to 8 months from the date that the Coast Guard accepts a complete application as required in this part. If the expiration date of the mariner's active credential is beyond 8 months of the date that the Coast Guard accepts a complete application as required in this part, the new credential issue date will be 8 months from the date of application acceptance at which time the currently active credential will become invalid in accordance with paragraph (d) of this section. Otherwise, the new credential issue validity date will coincide with the expiration date of the active credential held by the mariner. All other MMC transactions will be processed for immediate issuance.
(b) All endorsements, unless otherwise noted, are valid until the expiration date of the MMC on which they appear.
(c) A mariner may not serve under the authority of an MMC past its expiration date. An expired MMC may be renewed during an administrative grace period of up to 1 year beyond its expiration date as per § 10.227(h) of this part.
(d) When an MMC is renewed or re-issued before its expiration date in accordance with § 10.227, of this part the MMC that has been replaced becomes invalid unless otherwise noted in paragraph (a) of this section.
(e) An MMC is not valid until signed by the applicant and a duly authorized Coast Guard official.
(f) A mariner's endorsements authorize the holder to serve in any capacity endorsed on the MMC, or in any lower capacity in the same department, or in any capacity covered by a general endorsement thereon.
(g) If a mariner chooses to renew their license, MMD, COR, or STCW endorsement and receive their first MMC, the Coast Guard may also renew all other credentials for which the mariner is qualified.
(h) When a Document of Continuity is replaced with an MMC re-issued in accordance with § 10.227 of this part, the Document of Continuity that has been replaced becomes invalid. In the event that not all endorsements on a Document of Continuity are activated, a new Document of Continuity will be issued for the remaining endorsements.
Sections it refers to
The plain-English explanation on this page was written with AI from the regulation text above and checked automatically before publishing: every quote appears in the text, every number comes from it, and a second model confirmed each statement adds nothing the text doesn't say. Regulation text current as of March 31, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.