Everything you need to know about sanctions screening for ships: how to check if a vessel is sanctioned, the four lists that matter, the dark fleet, STS transfers, and the practices regulators look for.
To check if a ship is sanctioned, look up its IMO number on the OFAC SDN list, the UK OFSI Consolidated List, the EU Consolidated Financial Sanctions List, and the UN Security Council list. Or use an aggregated tool like Strait Up Maritime, which checks all four major lists plus regional lists in a single query against 2,893+ currently designated vessels and entities.
The reliable way to screen a vessel is to use its IMO number, not its name. Vessel names can be changed within days; IMO numbers are permanent for the life of the hull. Here is the standard six-step screening process compliance teams use:
To check if a ship is sanctioned, you need to look up its IMO number (a unique 7-digit vessel identifier) on the relevant authority's sanctions list. The four most consulted lists are: the U.S. Treasury OFAC Specially Designated Nationals (SDN) list, the UK OFSI Consolidated List, the EU Consolidated Financial Sanctions List, and the UN Security Council Consolidated List. Strait Up Maritime aggregates these into a single searchable database at api.straitupmaritime.com/sanctions where you can search by vessel name, IMO, or MMSI in seconds.
The Specially Designated Nationals and Blocked Persons (SDN) list is maintained by the U.S. Department of the Treasury's Office of Foreign Assets Control (OFAC). It identifies individuals, companies, vessels, and aircraft whose assets U.S. persons must block, and with whom U.S. persons are generally prohibited from dealing. Vessels appear on the SDN list with their IMO number, flag, tonnage, and the sanctions program under which they were designated (for example IRAN-EO13902 or RUSSIA-EO14024).
The 'dark fleet' (also called the 'shadow fleet' or 'shadow tanker fleet') refers to vessels — predominantly aging crude oil tankers — that operate outside mainstream maritime regulation to transport sanctioned cargoes. Common dark-fleet practices include disabling AIS transponders (going 'dark'), using flags of convenience, falsifying voyage documentation, conducting ship-to-ship (STS) transfers in international waters, and changing ownership through shell companies. The fleet primarily moves Iranian, Russian, and Venezuelan crude oil to buyers willing to accept sanctions risk.
A ship-to-ship (STS) transfer is the transfer of cargo (most commonly crude oil) from one vessel to another while at sea. STS transfers are a routine commercial practice but are also used by the dark fleet to obscure the origin of sanctioned cargoes. A vessel will load sanctioned crude in one location, sail to a recognised STS area, and transfer the cargo to a 'clean' tanker that will deliver it to the final buyer with paperwork suggesting a legitimate origin. OFAC and UK OFSI consider undisclosed STS transfers with sanctioned vessels a strong red flag for sanctions evasion.
A vessel 'goes dark' when it switches off or spoofs its Automatic Identification System (AIS) transponder. AIS is the system that broadcasts a vessel's position, identity, course, and speed for collision avoidance and traffic monitoring. Disabling AIS in non-emergency conditions is widely treated as a deceptive shipping practice and a sanctions-evasion red flag. OFAC's May 2020 sanctions advisory specifically calls out AIS manipulation as a high-risk indicator for sanctions screening.
OFAC publishes updates to the SDN list on an irregular schedule — sometimes several times per week, sometimes once a month, driven by enforcement actions and new designations. UK OFSI publishes consolidated list updates on a similar irregular cadence. The EU Council updates its Consolidated List in response to Council decisions, often in batches. UN designations follow Security Council resolutions. Strait Up Maritime ingests updates from these authorities daily and publishes any new designations as news articles within 24 hours.
OFAC (U.S. Treasury, Office of Foreign Assets Control) administers and enforces U.S. economic and trade sanctions, primarily extraterritorially through the dollar-clearing system. OFSI (UK HM Treasury, Office of Financial Sanctions Implementation) does the same for UK financial sanctions. The EU Consolidated Financial Sanctions List is maintained by the European Commission on behalf of the Council of the European Union. The three regimes are separate, and a vessel can be designated under one but not the others. Compliance teams typically screen against all four major lists (OFAC, OFSI, EU, UN) plus regional lists where they trade.
Yes. The OFAC SDN list, the UK OFSI Consolidated List, the EU Consolidated Financial Sanctions List, and the UN Security Council Consolidated List are all public records, published online by their issuing authorities and updated as designations are made. Each listing includes vessel identification (IMO, flag, tonnage), the sanctions program under which it was designated, and any addresses or alias names associated with it. Strait Up Maritime aggregates all of these into a single searchable database.
An IMO number is a globally unique 7-digit identifier assigned to a sea-going merchant vessel by IHS Markit on behalf of the International Maritime Organization (IMO). IMO numbers are permanent — they stay with the vessel for its entire life regardless of ownership change, name change, flag change, or hull modification. This makes IMO the most reliable identifier for sanctions screening, because while a vessel's name can be changed in days, the IMO cannot be changed at all. IMO numbers always follow the format 'IMO XXXXXXX' where X is a digit 0–9.
Sanctions screening obligations apply to a wide range of maritime industry participants: shipowners and operators, charterers, freight forwarders, ship managers, brokers, P&I clubs, classification societies, marine insurers, banks financing maritime trade, commodity traders, and bunker suppliers. The specific scope depends on jurisdiction. U.S. persons (including U.S. citizens, U.S. companies, and any person physically in the U.S.) must comply with OFAC sanctions worldwide. UK persons must comply with UK sanctions. Many sanctions regimes also have extraterritorial reach through the financial system.