The short answer
The Merchant Mariner Credential (MMC) is the U.S. Coast Guard document that shows what you're qualified to do aboard a U.S. vessel. Mariners still call it a "license," a "Z-card" or "papers," but since 2009 it has been one credential. Everything you hold goes on it as an endorsement, from Ordinary Seafarer to Master Unlimited, Wiper to Chief Engineer, and Tankerman to STCW Basic Training 46 CFR Part 10.
What it replaced, and what it looks like now
The MMC was first issued in 2009. It combined four older documents into one: the merchant mariner license (officers), the Merchant Mariner's Document or "Z-card" (ratings), the Certificate of Registry (staff officers such as pursers), and the STCW certificate.
For years it was a red, passport-style booklet with endorsement stickers. Since March 1, 2024, the Coast Guard issues it as a single sheet of tear-resistant synthetic paper. Booklets already issued stay valid until they expire, so you'll see both formats for a few more years.
What's on it: three kinds of endorsements
| Type | What it covers | Examples |
|---|---|---|
| National officer | Licensed deck and engine positions on U.S. vessels, with tonnage, horsepower and route limits | Master, Mate, Third Mate, OUPV, Chief Engineer, Third Assistant Engineer |
| National rating | Unlicensed positions | Ordinary Seafarer (formerly Ordinary Seaman), Wiper, Able Seafarer (AB), QMED, Tank Vessel-PIC / Tank Barge-PIC (formerly Tankerman), Lifeboat Operator (formerly Lifeboatman) |
| STCW | International qualifications for vessels on voyages covered by the STCW Convention | Basic Training, OICNW, RFPNW, Able Seafarer–Deck |
Read your endorsements closely. The route, tonnage or horsepower limits printed with them are what you can legally sail on, not the job title alone. See National vs. STCW and Vessel Tonnage & Your License.
What the MMC is not
- It isn't your medical certificate. Medical fitness is shown on a separate medical certificate, with its own expiration date. The older red booklets had a clear plastic sleeve inside the back cover to hold it. Today's single-sheet MMC has no holder, so keep your medical certificate with it yourself. See Medical Fitness.
- It isn't a TWIC. The TWIC is a separate TSA security card for access to secure port and vessel areas. See TWIC & First MMC.
- It isn't a job. Employers may add their own requirements, such as company training, drug-testing programs and medical checks.
How long it lasts
| Document | Validity |
|---|---|
| MMC | 5 years. National endorsements on it share the MMC's expiration date. |
| Medical certificate | Generally 5 years for national endorsements and 2 years for STCW service, so it can run out before your MMC does 46 CFR 10.301 |
| STCW endorsements | Some, such as Basic Training, must be revalidated every 5 years through sea service or refresher training. See the Basic Training update. |
If you're coming ashore for a while, you may be able to keep the credential in continuity instead of letting it lapse. See Renewal & Continuity.
How you get one
Check the basics first
Medical fitness, drug testing and your record. See Before You Spend Money.
Meet the endorsement's requirements
Sea service, training, and an exam or approved course, depending on what you're applying for.
Assemble the application
The CG-719B application, medical certificate application (CG-719K), drug-test proof, TWIC or an exemption statement if it applies, and fees.
The NMC evaluates it
The National Maritime Center reviews your application, including the safety and suitability review, and schedules any exams at a Regional Exam Center.
Check it when it arrives
Make sure every endorsement, limitation and date is correct. Errors are easier to fix right away.
Traps mariners hit with their MMC
- Letting the medical certificate lapse while the MMC is still valid. Without a valid medical certificate, you can't sail on the credential.
- Assuming a job title matches the endorsement. The route and tonnage limits decide what you can sail on.
- Forgetting STCW revalidation. STCW endorsements have their own requirements and can't be placed in continuity.
- No copies. Keep a scan of your MMC, medical certificate and sea-service records somewhere safe. Don't post photos of them online; they carry personal information.
- Waiting until the last month to renew. Apply well ahead; the NMC recommends about 90 days.
Your record requires an individual review
A past DUI, criminal conviction, drug-related matter, prior test result, prescription medication, or driving-record issue does not automatically mean you cannot become a mariner. It may, however, affect timing, documentation, safety-and-suitability review, credential issuance, renewal, or employment.
Mariners Online cannot determine your eligibility. Read the current Coast Guard application carefully, answer every question truthfully, obtain official records, and consult current NMC guidance or qualified individualized advice before applying if your history is complicated.
Official sources
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