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United States · Captain’s license

Merchant Mariner Credential (MMC): what it is and how to apply

The Merchant Mariner Credential is the Coast Guard document that holds all your qualifications as endorsements, from OUPV and Master to ratings and STCW endorsements. It replaced the separate Merchant Mariner’s Document, license and Certificate of Registry. A merchant mariner credential is valid for 5 years, and you apply for it to the Coast Guard with your sea service, medical and TWIC.

  • 1 documentReplaces licenses, MMDs and CORs
  • 12 monthsLife of an approved application
  • March 1, 2024Start of the single-page credential
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Updated October 2026 · Written from official sources, listed at the bottom of this page

What is a merchant mariner credential?

It’s one credential with endorsements on it. An MMC lets you serve in any capacity endorsed on it, or in any lower capacity in the same department. Licenses, MMDs and Certificates of Registry are no longer issued as separate documents, so a captain’s license today is an officer endorsement on an MMC.

Your TWIC from TSA is your main identification document, and you must keep both and show them to an authorized official when asked. Your medical certificate is issued separately from the MMC.

The merchant mariner credential application

You apply as an original for your first credential, after letting one lapse past the grace period, or after one was revoked. The application can go in person, by mail or electronically, and you can apply at any Regional Examination Center or another location the Coast Guard designates. It stays valid for 12 months after the Coast Guard approves it, and an incomplete one may not be processed.

The Coast Guard issues the credential only after its criminal record review and National Driver Register check, a passed drug test and proof of a valid TWIC.

What goes in the application →The six steps in order →

The credential itself

Since March 1, 2024, the Coast Guard has issued the MMC as a single two-sided page on tear- and water-resistant synthetic paper, in place of the old passport-style book. A passport-style MMC stays valid until it expires, and you get the new style at your next credential transaction. The Coast Guard asked mariners not to request a new MMC unless theirs is lost, damaged or close to expiring.

If yours is lost, you can get a duplicate without an exam by applying with an affidavit that describes the loss. The duplicate has the same authority and expiration date, and there’s no fee for one lost in a marine casualty.

Checking your application status

The National Maritime Center (NMC) in Martinsburg, West Virginia, handles applications, and it publishes how to check an application’s status, along with the current forms and checklists. You can email it at IASKNMC@uscg.mil.

National Maritime Center ↗Renewing your MMC →
Sources: eCFR · Federal Register · National Maritime Center and 3 more. Checked October 2026.

Rules and fees can change, so check the official site before your test.

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