46 CFR 10.207: Mariner identification number for MMC records

Last reviewed: October 14, 2026

This section says what identification number is used for a mariner's MMC. For recordkeeping purposes only, the official number is the individual's social security number. The credential itself shows a unique serial number called the mariner reference number.

What it says

  1. For recordkeeping purposes only, a mariner's official MMC identification number is the individual's social security number.

    “For recordkeeping purposes only, a mariner's official MMC identification number is the individual's social security number.”

  2. A unique serial number, called the mariner reference number, appears on the credential, and the social security number does not appear on it.

    “However, a unique serial number, called the mariner reference number, and not the social security number, will appear on the credential.”

Common questions

What is my official MMC identification number?

For recordkeeping purposes only, your official MMC identification number is your social security number.

“For recordkeeping purposes only, a mariner's official MMC identification number is the individual's social security number.”

Does my social security number appear on my MMC?

No. A unique serial number called the mariner reference number appears on the credential instead of the social security number.

“However, a unique serial number, called the mariner reference number, and not the social security number, will appear on the credential.”

The text of 46 CFR 10.207

Electronic Code of Federal Regulations (eCFR), current as of April 16, 2026 · Read it on eCFR

Identification number

For recordkeeping purposes only, a mariner's official MMC identification number is the individual's social security number. However, a unique serial number, called the mariner reference number, and not the social security number, will appear on the credential.

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 April 16, 2026. The regulation text governs. RegKnot is not affiliated with the U.S. Coast Guard.