Do I need separate insurance specifically for STS operations, or does my existing cover extend?

In most cases your existing hull, cargo, and P&I cover can extend to STS operations — but only if the operation was disclosed at placement and falls within your trading warranties and navigating limits. If your policy was placed without reference to STS activity, you should seek written confirmation from your broker that cover attaches before the operation. Some underwriters will require an endorsement or an additional premium for regular STS programmes. Do not assume cover extends; confirm it in writing.

What happens if the STS transfer causes a pollution incident in Singapore waters?

MPA will respond immediately and may direct clean-up operations at your expense. Your P&I entry should cover the clean-up costs, third-party claims, and any fines that are insurable under Singapore law (note: fines imposed as a penalty for regulatory breaches are generally not insurable). You must notify your P&I insurer as soon as the incident occurs — delay in notification can prejudice your cover. If the incident involves oil from a tanker, the CLC and Fund Convention framework will also apply, and your P&I club will manage the CLC claim process on your behalf.

Does my cargo insurance cover shortage or contamination that occurs during an STS transfer?

ICC (A) cover should respond to shortage or contamination caused by an insured peril during an STS transfer, provided the transfer was disclosed at placement and conducted in accordance with the voyage terms. However, losses attributable to inherent vice of the cargo, inadequate packaging, or the nature of the commodity itself are excluded. If the transfer was not disclosed or took place outside the agreed transit route, underwriters may argue the loss occurred during an uninsured deviation. Disclose the STS at placement and keep full transfer records.

What do you need from me to bind cover for a vessel conducting regular STS operations?

At a minimum: vessel particulars (name, flag, class, GT, year built), current P&I entry details, a copy or summary of your STS plan, the trading area and typical counterparty vessel profile, cargo types and approximate annual throughput, and your loss history for the past five years. For one-off STS operations, we also need the specific location, the mooring master's details, and confirmation of MPA or coastal state notification. The more complete the information, the faster we can approach underwriters and the broader the cover terms we can negotiate.

How long does it take to bind cover or get confirmation that an STS operation is covered?

For an endorsement to an existing policy confirming STS cover, we can typically obtain underwriter confirmation within one to two business days if the information is complete. For a new placement that includes STS as a core feature of the risk, allow five to seven business days for the full market approach. Do not schedule an STS operation and then seek insurance confirmation the day before — underwriters will note the time pressure and it rarely produces the best terms.

What happens if the counterparty vessel in the STS is not classed or has an expired P&I entry?

This is a significant red flag for both regulatory and insurance purposes. An unclassed vessel may not be permitted to conduct STS operations under MPA rules, and its owner may have no P&I cover to respond to third-party claims arising from the transfer. Your own hull and P&I cover will not be affected by the counterparty's insurance status, but your practical recovery position in the event of a collision or pollution incident will be severely weakened if the other vessel is uninsured. Always verify the counterparty vessel's class certificate and P&I entry before agreeing to an STS operation.

Are Ship-to-Ship Transfers Legal? Cover Guide

Written by the Singapore Marine Insurance editorial team · reviewed by Anton Kuznetsov, founder

Ship-to-ship (STS) transfers are a routine part of APAC trade — crude and refined products lightered off Singapore's OPL anchorages, LNG shifted between FSRUs, bulk commodities transhipped through the Malacca and Singapore Straits. The short answer to whether they are legal is: yes, under the right conditions. The longer answer is that legality depends on where the transfer happens, which flag states and port authorities have jurisdiction, and whether your vessel, your cargo policy, and your P&I entry are structured to respond when something goes wrong mid-transfer. This guide is for owners, ship managers, freight forwarders and cargo interests who need to understand the compliance framework and the insurance gaps before the operation begins — not after a spill or a cargo loss.

The Legal Framework Governing STS Transfers

STS transfers are governed by a layered set of international and domestic rules. At the international level, MARPOL Annex I Regulation 41 requires that any STS transfer of oil between tankers at sea follow an approved Ship-to-Ship Transfer Plan, and that the operation be notified to the relevant coastal state authority at least 48 hours in advance. IMO Resolution MEPC.186(59) provides the operational guidelines that most flag states have incorporated into their domestic frameworks.

In Singapore waters — including the port limits and the OPL anchorage areas — the Maritime and Port Authority of Singapore (MPA) is the competent authority. MPA requires advance notification, approval of the STS plan, and in many cases the presence of a licensed mooring master. Transfers conducted within Singapore port limits without MPA clearance are not merely an insurance problem; they are a regulatory offence that can result in vessel detention, fines, and loss of port privileges. If your operation sits in Indonesian or Malaysian waters, the respective maritime authorities apply their own notification regimes, and the MPA clearance you obtained does not carry across.

For non-oil cargoes — containers, bulk, LNG, LPG — there is no single MARPOL equivalent, but IMO's International Safety Management (ISM) Code still applies. Your vessel's Safety Management System (SMS) must include procedures for STS operations. An STS transfer conducted outside the SMS procedures is an ISM non-conformity, which your P&I club will note when assessing whether to support a claim arising from the operation.

Flag state law adds another layer. A vessel flagged in Panama, Marshall Islands, or the Bahamas must comply with that flag state's STS regulations in addition to MARPOL and any coastal state requirements. Where flag state rules are silent, the IMO guidelines fill the gap — but 'silent' is not the same as 'permissive'. Your ship manager should confirm the flag state position in writing before each STS programme, particularly for operations in disputed or sensitive areas such as the South China Sea.

Where Your Hull Cover Stands During an STS Operation

Standard Institute Time Clauses — Hulls (ITC-H 1/10/83) and the more recent International Hull Clauses (IHC 2003) both cover collision and contact damage, but the devil is in the trading warranties and the navigation limits endorsed onto your policy. If your vessel is operating outside its agreed trading area — for example, conducting an STS in a zone not covered by your navigating limits — the underwriter has grounds to decline a hull claim arising from that operation.

The Inchmaree clause, which is incorporated into both ITC-H and IHC, extends cover to loss or damage caused by negligence of the master, officers, or crew, provided the loss is not attributable to want of due diligence by the assured. This matters in an STS context because contact damage between the two vessels during mooring or cargo transfer is one of the most common loss events. If the mooring master was negligent but your vessel was otherwise seaworthy and the operation was properly authorised, the Inchmaree clause should respond. If the operation was conducted without the required MPA notification or outside your SMS procedures, underwriters will argue that want of due diligence applies.

Running-down clause (RDC) cover under your hull policy responds to your liability for damage to the other vessel in a collision — but only up to three-quarters of the liability in most standard wordings. The remaining quarter, and any liability that exceeds the hull policy's collision limit, falls to your P&I entry. Make sure your hull and P&I cover are placed with full awareness of each other's limits; a gap between the two is a real exposure in a high-value STS collision.

If your vessel is on a lay-up return or operating under a restricted navigation endorsement at the time of the STS, contact your broker before the operation. Underwriters will not simply waive a navigation warranty after a loss has occurred.

Cargo Insurance: What the Institute Clauses Say About STS

Institute Cargo Clauses (A) provide the broadest all-risks cover and are the starting point for most bulk liquid and high-value cargo shipments through Singapore. However, ICC (A) cover attaches from warehouse to warehouse on the basis of the voyage declared at inception. An STS transfer that was not disclosed at the time of placing — or that takes place outside the geographic scope of the policy — can give underwriters grounds to treat the transfer leg as an uninsured deviation.

The transit clause in ICC (A) does contemplate transhipment, but it requires that the transhipment be a necessary and customary part of the transit. A planned STS that is integral to the commercial structure of the voyage — for example, a VLCC lightening cargo to a smaller vessel for port entry — should be disclosed at placement so the underwriter can confirm cover attaches through the transfer. An opportunistic STS arranged mid-voyage without prior disclosure is a different matter.

For bulk liquid cargoes, contamination and shortage are the primary cargo claims arising from STS operations. ICC (A) covers both, subject to the inherent vice exclusion and the insufficiency of packing exclusion. If your cargo is transferred between tanks using the receiving vessel's pumping system and arrives short or contaminated, the cause of loss investigation will focus on whether the loss arose from a peril insured against or from the nature of the cargo itself. Your broker should ensure the policy wording does not contain a blanket exclusion for losses arising during STS operations — some cargo policies in the Singapore market carry such endorsements for specific commodity types.

Freight forwarders and traders who hold cargo interests but do not control the vessel should pay particular attention to the Hague-Visby Rules position. Under bills of lading governed by Hague-Visby, the carrier's liability for cargo loss or damage is subject to package or unit limits that may be far below the commercial value of the cargo. Your cargo insurance is your primary recovery mechanism; the carrier's liability is a secondary and often inadequate remedy. This is especially true where the STS is conducted OPL and the bill of lading is issued on terms that limit the carrier's liability to the statutory minimum.

P&I Cover and the STS Operation

Your P&I entry covers third-party liabilities that fall outside the hull policy: cargo claims from the receiver, pollution liability, wreck removal, crew injury, and the quarter of collision liability not picked up by the RDC. All of these exposures are heightened during an STS operation. A bunker spill or cargo overflow during transfer can trigger MARPOL enforcement, coastal state clean-up demands, and civil claims from third parties — all of which your P&I club needs to be notified of promptly.

Most International Group P&I clubs include STS operations within standard entry, but they attach conditions. The operation must comply with the IMO STS guidelines, the vessel's SMS must include STS procedures, and in many cases the club requires that a qualified mooring master be engaged for oil transfers above a specified quantity. If your vessel is entered with a fixed-premium P&I insurer rather than a mutual club — which is common for smaller vessels and regional operators in Singapore — check the policy wording carefully. Fixed-premium P&I policies frequently exclude or sub-limit pollution liability arising from STS operations.

Pollution liability in APAC waters is a significant exposure. Singapore is party to the CLC (Civil Liability Convention) and the Fund Convention, which provide a compensation framework for oil pollution from tankers. However, CLC cover is channelled through the shipowner's compulsory insurance — your P&I entry — and the CLC limits under the 1992 Protocol are calculated by reference to the vessel's gross tonnage. If your P&I entry does not provide CLC-compliant cover, or if the STS operation falls outside the scope of your entry, you are personally exposed to pollution claims that can exceed the LLMC limitation fund.

General average is another P&I-adjacent issue. If an STS operation goes wrong and a general average act is declared — for example, cargo is jettisoned to prevent a fire spreading between vessels — the York-Antwerp Rules govern the adjustment. Your cargo interests will be required to contribute to the general average fund before cargo is released. Make sure your cargo policy includes a general average clause and that the policy limit is sufficient to cover both the cargo value and a potential GA contribution.

What to Disclose and When: Placing STS Cover in Singapore

The MAS-regulated insurance market in Singapore operates on the principle of utmost good faith (uberrimae fidei), codified in the Marine Insurance Act (Cap. 387). Your duty of disclosure requires you to tell your broker — and through your broker, the underwriter — every material fact that would influence a prudent underwriter's decision to accept the risk or set the premium. An STS programme is a material fact. Disclose it at inception, not after a loss.

When you approach us to place or renew cover that includes STS operations, bring the following to the conversation so we can present the risk accurately to underwriters and secure the broadest available cover:

The notification and approval process with MPA (or the relevant coastal state authority) should be completed before the operation, not treated as a formality. Keep copies of all approvals, the STS plan, the mooring master's certificate, and the pre-transfer safety checklist. These documents are your first line of defence if a claim is disputed.

Details of the vessels involved: flag, class, age, gross tonnage, and current P&I entry
The STS plan, including the location (OPL coordinates or named anchorage), the cargo type and quantity, and the transfer method
Confirmation that the operation has been or will be notified to MPA or the relevant coastal state authority
The name and qualifications of the mooring master engaged for the operation
Any prior STS loss history on the vessels involved in the last five years
The bill of lading terms and the governing law of the contract of carriage

High-Risk STS Zones and War / Sanctions Considerations

Not all STS transfers carry the same risk profile. Operations conducted in the Singapore Strait and the established OPL anchorages off Batam operate under a well-understood regulatory framework and are generally insurable on standard terms. Operations in less-regulated waters — the South China Sea beyond the established anchorages, the Gulf of Thailand, or waters adjacent to sanctioned jurisdictions — attract additional underwriting scrutiny.

The Joint War Committee (JWC) Listed Areas are updated periodically and affect both hull war cover and cargo war cover. If your STS operation takes place in or near a JWC-listed area, your standard hull and cargo policies will exclude war and piracy risks unless you have purchased separate war cover. For APAC operators, the relevant areas to monitor include parts of the South China Sea and waters near the Korean peninsula. Your broker should be checking the current JWC list at each renewal and at any point you are considering an STS in an unfamiliar area.

Sanctions are a separate but related concern. An STS transfer involving a vessel that is on the OFAC SDN list, the EU consolidated sanctions list, or the MAS sanctions list will not be insurable in the Singapore market — and participating in such a transfer may expose you to criminal liability under Singapore's Monetary Authority of Singapore Act and related regulations. Before any STS involving a counterparty vessel you have not previously dealt with, conduct a sanctions screening on the vessel, its owner, and its operator. Your broker can assist with this process, but the primary obligation rests with you as the contracting party.

Frequently asked questions

Do I need separate insurance specifically for STS operations, or does my existing cover extend?: In most cases your existing hull, cargo, and P&I cover can extend to STS operations — but only if the operation was disclosed at placement and falls within your trading warranties and navigating limits. If your policy was placed without reference to STS activity, you should seek written confirmation from your broker that cover attaches before the operation. Some underwriters will require an endorsement or an additional premium for regular STS programmes. Do not assume cover extends; confirm it in writing.
What happens if the STS transfer causes a pollution incident in Singapore waters?: MPA will respond immediately and may direct clean-up operations at your expense. Your P&I entry should cover the clean-up costs, third-party claims, and any fines that are insurable under Singapore law (note: fines imposed as a penalty for regulatory breaches are generally not insurable). You must notify your P&I insurer as soon as the incident occurs — delay in notification can prejudice your cover. If the incident involves oil from a tanker, the CLC and Fund Convention framework will also apply, and your P&I club will manage the CLC claim process on your behalf.
Does my cargo insurance cover shortage or contamination that occurs during an STS transfer?: ICC (A) cover should respond to shortage or contamination caused by an insured peril during an STS transfer, provided the transfer was disclosed at placement and conducted in accordance with the voyage terms. However, losses attributable to inherent vice of the cargo, inadequate packaging, or the nature of the commodity itself are excluded. If the transfer was not disclosed or took place outside the agreed transit route, underwriters may argue the loss occurred during an uninsured deviation. Disclose the STS at placement and keep full transfer records.
What do you need from me to bind cover for a vessel conducting regular STS operations?: At a minimum: vessel particulars (name, flag, class, GT, year built), current P&I entry details, a copy or summary of your STS plan, the trading area and typical counterparty vessel profile, cargo types and approximate annual throughput, and your loss history for the past five years. For one-off STS operations, we also need the specific location, the mooring master's details, and confirmation of MPA or coastal state notification. The more complete the information, the faster we can approach underwriters and the broader the cover terms we can negotiate.
How long does it take to bind cover or get confirmation that an STS operation is covered?: For an endorsement to an existing policy confirming STS cover, we can typically obtain underwriter confirmation within one to two business days if the information is complete. For a new placement that includes STS as a core feature of the risk, allow five to seven business days for the full market approach. Do not schedule an STS operation and then seek insurance confirmation the day before — underwriters will note the time pressure and it rarely produces the best terms.
What happens if the counterparty vessel in the STS is not classed or has an expired P&I entry?: This is a significant red flag for both regulatory and insurance purposes. An unclassed vessel may not be permitted to conduct STS operations under MPA rules, and its owner may have no P&I cover to respond to third-party claims arising from the transfer. Your own hull and P&I cover will not be affected by the counterparty's insurance status, but your practical recovery position in the event of a collision or pollution incident will be severely weakened if the other vessel is uninsured. Always verify the counterparty vessel's class certificate and P&I entry before agreeing to an STS operation.

If you are planning an STS operation or need to review whether your existing hull, cargo, or P&I cover responds correctly, speak to our Singapore-based team before the operation begins. Bring your STS plan, vessel details, and cargo particulars and we will present the risk to specialist underwriters on your behalf and confirm exactly where your cover stands.