Ocean carrier SCAC codes and MBL prefixes

What is the difference between a SCAC and an MBL prefix?

A SCAC (Standard Carrier Alpha Code) is a two-to-four-letter company code issued by NMFTA. US vessel-manifest rules require the issuer’s SCAC at the start of the bill number reported to CBP, followed by up to 12 letters or digits (19 CFR 4.7a). The printed bill, carrier identification and filing reference can differ. MSC’s MEDU notice illustrates why a prefix must not be normalized merely by adding another carrier code. Confirm the issued reference and the receiving system’s instructions.

Why can a correct-looking code point to the wrong carrier?

The first four letters are a strong clue, not proof. These are the usual reasons a plausible code still misleads:

• House bills start with the forwarder's or NVOCC's SCAC, not the ocean carrier's.
• Groups such as Maersk, CMA CGM and COSCO issue bills under more than one brand and code.
• Prefixes change: Yang Ming moved from YMLU to YMJA in October 2023, and K Line, MOL and NYK container bills became ONE bills in 2018.
• A container owner code such as MSKU is not a bill prefix, even when the same carrier owns the box.
• Codes change. Confirm a live SCAC with NMFTA before filing.

How do you check an MBL reference before filing or tracking?

Six checks keep a plausible four-letter value from attaching the wrong carrier or document to a shipment:

• Confirm whether the document is a house bill or a master bill.
• Copy the issuing carrier's legal name and the full bill reference exactly as printed.
• Keep the carrier code, bill body, booking number and container number in separate fields.
• Verify an uncertain or time-sensitive SCAC with NMFTA.
• Test the complete reference in the carrier or filing system that will receive it.
• Store the original document next to any normalized value so later users can trace the change.

How is this directory checked?

Each code was checked on October 3, 2026 against three kinds of evidence, strongest first: the carrier's own documents (advisories, bill and EDI guides, tracking pages) or its filings with the US Surface Transportation Board; the UIIA equipment provider list dated September 4, 2026; and, where neither exists, at least two independent references such as US import manifest records and carrier code lists. Codes found in only one independent source were left out. Each row shows its evidence level and links to up to three sources.

A UIIA code identifies the carrier for equipment interchange and is not always its bill prefix: OOCL appears in the UIIA list as OOLL, while its bills use OOLU.