The Merchant Mariner Credential (MMC) is a booklet-style document issued by the USCG NMC that serves as the single holder for every license and endorsement a mariner earns. Before 2014, captains carried a separate Z-card (seaman's record book) and a distinct license document; the MMC combined both. If you hold an OUPV, a Master, an AB endorsement, or any other federal mariner credential issued after 2014, it is in your MMC.
What the MMC contains
The MMC shows the mariner's credentials on individual pages, each listing the endorsement, the scope (tonnage, route, propulsion type), and the expiration date. A Master 100 GT Near Coastal with Sailing Endorsement is a separate page from an OUPV Near Coastal. Sea service is logged in the back of the booklet (for mariners who maintain a paper record; increasingly this is done electronically through the NMC's Mariner Registry system).
Expiration and renewal
Most MMC endorsements expire five years from the date of issuance. Renewals can be started up to a year before expiration and must be submitted through the NMC's online portal at dco.uscg.mil/nmc. Renewal requires a current physical exam, proof of required training or refresher courses, TWIC on file, and a drug testing compliance verification. The application fee varies by the number of endorsements being renewed.
Working with an expired MMC
Operating a commercial vessel with an expired license is a federal violation. The USCG can issue a civil penalty and revoke the credential. There is no grace period; if your MMC expired last month, you are unlicensed. If your credential is close to expiration and you have not started the renewal process, start now — processing times at the NMC vary from a few weeks to several months depending on workload and whether additional sea service review is required.
Upgrade during renewal
Renewals are a common time to apply for an upgrade — from OUPV to Master 25 GT, or from 25 GT to 50 GT. Submit the upgrade application alongside the renewal; they are processed together. You must meet the sea service and examination requirements for the higher endorsement.
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