The Fuel Oil Non-Availability Report (FONAR) and the Bunker Delivery Note (BDN) form the two-document paper trail that defines how a vessel proves sulphur compliance, or defends its failure to achieve it, under MARPOL Annex VI. They serve different functions. The BDN is the permanent record of what fuel was put aboard: its sulphur content, density, quantity, and the supplier declaration that the fuel met Reg 14 at the point of delivery. The FONAR is the record of what happened when compliant fuel simply wasn’t there to be bought. Together they constitute the documentary baseline that port state control (PSC) inspectors, flag administrations, and courts of arbitration use when they examine whether a vessel was operating within the law.
This article addresses both documents through the lens of MARPOL Annex VI sulphur compliance: what each document contains, the regulatory instruments that define them, how the MARPOL-delivered representative sample ties the BDN to a testable chain of custody, how the test-tolerance thresholds in MEPC.1/Circ.864 work in practice, and what a master and a shipowner need to understand about the limits of a FONAR as a legal defence. ISO 8217 fuel quality parameters, the BDN content requirements enumerated by Reg 18 itself, and the Singapore MFM delivery system are covered in the companion article MARPOL Annex VI Reg 18: bunker delivery note. Fuel-switching changeover procedures are covered in fuel switching operations. Fuel quality disputes and the ISO 8217 grade limits are covered in bunker quality and ISO 8217.
The regulatory architecture: Reg 14 and Reg 18
MARPOL Annex VI’s sulphur regime has two operational regulations. Regulation 14 sets the limits. Regulation 18 sets the documentation and verification framework.
Regulation 14: the sulphur limits
MARPOL Annex VI Regulation 14, as revised by the 2008 amendments entering force 1 July 2010 and subsequently amended by IMO Resolution MEPC.280(70) adopted 28 October 2016, establishes two global sulphur limits for fuel oil used for combustion on board ships engaged in international voyages:
The global cap is 0.50% m/m sulphur, in force from 1 January 2020. It replaced the previous 3.50% global limit. The 2020 date was set by MEPC.280(70) after MEPC.70 confirmed in October 2016 that sufficient compliant fuel would be available; the original Annex VI text had allowed for a possible 2025 implementation if supply was found inadequate.
The ECA limit is 0.10% m/m sulphur, in force in designated Emission Control Areas from 1 January 2015. The current designated SOx ECAs are: the Baltic Sea ECA (designated 2005, 0.10% from 2015), the North Sea ECA including the English Channel (designated 2005, 0.10% from 2015), the North American ECA (effective 1 August 2012), the United States Caribbean Sea ECA (effective 1 January 2013), and the Mediterranean Sea ECA (effective 1 May 2025 under Resolution MEPC.361(79) adopted 16 December 2022).
A vessel with an approved exhaust gas cleaning system (EGCS) fitted and operating within its certified parameters is treated as compliant under Regulation 4 of MARPOL Annex VI regardless of the sulphur content of the fuel it burns, because the EGCS brings the exhaust SOx to the equivalent of what compliant fuel would produce.
Regulation 14.1.3: the carriage ban
IMO Resolution MEPC.305(73), adopted 26 October 2018 and in force 1 March 2020, added Regulation 14.1.3: a prohibition on carrying fuel oil with a sulphur content above 0.50% m/m for combustion purposes on board a ship that does not have an approved EGCS. This is the carriage ban, and it changed the enforcement dynamic fundamentally.
Before March 2020, a PSC inspector who found non-compliant fuel on board had to prove the ship had burned it. After March 2020, the mere presence of non-compliant fuel in a combustion tank on a ship without a scrubber is itself the violation. The PSC inspector’s job became simpler: sample the in-use fuel from the fuel service system, verify the sulphur content, and the detention case is made without any reference to whether the ship had previously filed a FONAR.
The carriage ban does not apply to fuel carried as cargo or in a dedicated cargo tank of a product tanker. It applies to fuel in service tanks, settling tanks, day tanks, or any tank from which fuel is drawn for combustion by the main engine, auxiliary engines, boilers, or incinerators.
Regulation 18: the BDN and the MARPOL sample
Regulation 18 was substantially rewritten by the 2008 MARPOL Annex VI amendments (MEPC.176(58)). Its core provisions are:
Regulation 18.5 requires the bunker supplier to deliver a BDN to the receiving vessel. The BDN must be retained on board for three years.
Regulation 18.8, as amended by MEPC.250(66) in 2014, requires that a representative sample of the fuel oil delivered to the ship be drawn at the ship’s manifold throughout the bunker transfer using a continuous-flow drip sampler. This sample is sealed and signed by the supplier representative and the ship’s officer in each other’s presence. It is the MARPOL-delivered representative sample. It must be retained on board for 12 months from the date of delivery, or until the fuel is consumed in its entirety if that is later.
Regulation 18.2 establishes the non-availability procedure that generates the FONAR.
The BDN sulphur figure is a supplier declaration of the sulphur content of the fuel at the time of delivery. It is not a test result from the specific parcel delivered to that vessel; it is typically based on the supplier’s pre-delivery testing of the bunker tank cargo. The MARPOL-delivered sample is the means by which that declared value can be independently verified, because it is a sample of the exact parcel that entered the ship’s tanks, drawn in a legally defensible manner.
The Bunker Delivery Note in the PSC sulphur-verification chain
What the BDN proves and what it does not
The BDN’s sulphur declaration is the starting point for compliance verification, not the end point. A PSC inspector who finds a BDN declaring 0.48% m/m sulphur has established that the supplier certified compliance. That certification does not, by itself, prove the fuel in the ship’s tanks has 0.48% m/m sulphur. Fuel can be blended, transferred, or contaminated after delivery. Multiple deliveries can be mingled in a tank. And suppliers occasionally mis-state the sulphur content, whether through error or fraud.
The BDN does prove three things that matter in a PSC inspection:
First, it proves the vessel received a delivery with a documented sulphur content on a specific date at a specific port. That creates an audit trail that can be reconciled against the fuel oil record book and the engineering log to track whether the vessel has a plausible story about where its current in-use fuel came from.
Second, the BDN’s three-year retention requirement gives PSC inspectors access to the complete delivery history of the vessel’s fuel since its last drydock or port call far enough back to identify any pattern of non-compliant procurement.
Third, the sealed MARPOL-delivered sample tied to the BDN by the same seal numbers and vessel/IMO/date markings is the primary physical evidence for resolving any dispute about whether the delivered fuel was compliant. When a PSC inspector requests testing of an in-use sample and the result is borderline, the MARPOL-delivered sample from the relevant BDN is sent to an accredited laboratory for independent analysis.
The three sample types and their roles
Three distinct fuel sample types appear in sulphur compliance inspections, and they have different regulatory statuses.
| Sample type | Where drawn | Retention period | Regulatory basis | PSC evidential status |
|---|---|---|---|---|
| MARPOL-delivered sample | Ship’s manifold, during transfer, continuous drip sampler | 12 months from delivery (or until fuel consumed) | Reg 18.8 and MEPC.182(59) | Primary; the definitive record of what was delivered |
| In-use sample | Fuel service system (fuel line or pump discharge) | No mandatory retention; used for immediate testing | MEPC.1/Circ.864 | Secondary; establishes what is currently being burned |
| Onboard sample | Ship’s bunker tank | No mandatory retention; used for immediate testing | MEPC.1/Circ.864 | Secondary; useful for tracing fuel source |
The MARPOL-delivered sample is the only one drawn under a documented chain-of-custody procedure with both parties present. If a dispute reaches arbitration or a flag state prosecution, that sample is the evidence that matters.
The test-tolerance thresholds under MEPC.1/Circ.864
IMO MEPC.1/Circ.864, issued 6 June 2018 and still in force, established the test uncertainty allowances that PSC inspectors and flag states use when evaluating in-use and onboard sample results.
For the 0.50% global sulphur cap, the tolerance threshold is 0.53% m/m. A test result at or below 0.53% m/m on an in-use or onboard sample is treated as compliant with the 0.50% cap when the measurement uncertainty of the test method (ISO 14596 or ASTM D4294 at the 95% confidence level) is taken into account.
For the 0.10% ECA sulphur limit, the tolerance threshold is 0.11% m/m. A result at or below 0.11% m/m on an in-use or onboard sample is treated as compliant with the 0.10% ECA limit.
These tolerances do not apply to the BDN declared sulphur value. A supplier cannot deliver fuel declared at 0.52% m/m sulphur and claim compliance with the 0.50% cap on the ground that the test tolerance makes it acceptable. The BDN declaration must be at or below 0.50% m/m (or 0.10% m/m for ECA-grade fuel). The tolerance framework applies at the verification stage, when the fuel is already on board and is being tested by a PSC inspector or flag state surveyor.
Expressed as inline relationships: a delivered fuel declared at is compliant at supply. When tested in use, a result is treated as consistent with the 0.50% cap at a 95% confidence level. For ECAs, at supply; in use.
The practical implication is that a ship burning a VLSFO declared at, say, 0.49% m/m on the BDN, but tested in use at 0.51% m/m, is likely within the test tolerance and will not be found non-compliant by a PSC inspector applying Circ.864. A result of 0.56% m/m on the same ship is unambiguously outside the tolerance and warrants further action.
PSC sulphur inspection sequence
Paris MoU and Tokyo MoU published guidance (MEPC.1/Circ.880, issued 1 October 2019) describes the recommended sequence for PSC officers verifying fuel oil sulphur compliance. The sequence has three stages:
Documentary check: the PSC inspector examines the BDN for the fuel currently in use. The inspector verifies the BDN is present and complete (supplier details, IMO number, date, quantity, density, sulphur content, flash point, and the Regulation 14 and 18.3 compliance declaration), that the fuel oil record book entries match the BDN delivery sequence, and that the retained MARPOL-delivered sample has intact tamper-evident seals with seal numbers matching the BDN endorsement.
In-use sample: if the documentary check raises concerns, or as a routine verification step, the inspector may take an in-use fuel sample from the fuel service system. The sample goes to an accredited laboratory (commonly a port-based testing facility or a laboratory approved by the flag state or the PSC MoU). Results below the tolerance threshold require no further action. Results above the threshold move to the next stage.
MARPOL-delivered sample testing: if the in-use result exceeds the tolerance threshold, the MARPOL-delivered sample from the relevant BDN is retrieved and sent for independent testing at an accredited laboratory. If that result also exceeds the tolerance, the ship has a sulphur non-compliance case to answer. The PSC inspector’s next steps depend on whether the in-use sulphur exceedance results from consumption of the same parcel as the non-compliant sample, or whether the fuel has been mixed with other deliveries since that BDN.
The MARPOL-delivered sample is the decisive evidence in this chain. A ship that can produce intact, correctly labelled, sealed samples for every BDN covering its current fuel inventory is in a dramatically better position than one that cannot. MEPC.1/Circ.880 makes explicit that where the MARPOL-delivered sample does not confirm non-compliance, the PSC inspector is expected to accept the sample result over the in-use test result.
Consequences of BDN deficiencies
PSC detentions on sulphur grounds typically involve one or more of:
- Missing BDNs for some or all of the current fuel inventory, making source tracing impossible.
- BDN sulphur content above the applicable limit (global or ECA), with no FONAR on file.
- MARPOL-delivered sample with broken, missing, or defaced seals, or seal numbers not matching the BDN, destroying the chain of custody.
- In-use sample sulphur content above the test-tolerance threshold with no credible explanation traceable to the BDN history.
- Fuel oil record book entries that don’t reconcile with the BDNs on board, suggesting unreported fuel or falsified records.
The Paris MoU deficiency code for BDN deficiencies is 18402 (fuel oil BDN missing or non-compliant). Tokyo MoU uses the same coding structure. A vessel detained under the carriage ban under Regulation 14.1.3 will also attract the broader deficiency code covering the substantive MARPOL violation. Both deficiency types are recorded in the PSC information exchange systems (THETIS-EU for Paris MoU, APCIS for Tokyo MoU) and remain visible to inspectors at subsequent ports.
The Fuel Oil Non-Availability Report (FONAR)
Regulation 18.2 and what it actually says
MARPOL Annex VI Regulation 18.2 states that when a ship cannot comply with the applicable sulphur limit under Regulation 14 because the required fuel is not available, the master shall notify the flag state administration and the relevant authority of the port of destination. The ship is required to document the efforts made to obtain compliant fuel and the reason why compliant fuel could not be obtained. The Administration and the port authority may then take any steps they consider appropriate.
Three things are explicit in the regulation and are often misunderstood in practice:
First, the regulation does not grant an exemption. It grants a procedure for documenting non-compliance. The PSC inspector and the flag state retain full discretion to accept or reject the FONAR, and to impose consequences regardless.
Second, the burden of demonstrating non-availability lies with the ship, not with the authority. The ship must show that it made a genuine, documented, commercial effort to procure compliant fuel and was unable to do so. A FONAR filed without supporting documentation of specific supplier inquiries and refusals will likely be rejected.
Third, the regulation requires notification to both the flag state and the port of destination. Filing with only one is not sufficient. IMO guidance is that the notification should be made as early as practicable, before the ship enters the area where the compliant fuel is required.
MEPC.1/Circ.878: the 2019 standard FONAR format
IMO MEPC.1/Circ.878, issued 29 March 2019, superseded MEPC.1/Circ.864’s earlier FONAR guidance and established a standardized FONAR format. The standardised form requests the following information:
Vessel particulars: vessel name, IMO number, flag state, call sign, type of vessel, gross tonnage, deadweight, propulsion fuel type normally used, type of EGCS fitted (if any).
Voyage details: departure port and date, destination port and estimated date of arrival, the relevant compliance zone entered (global cap area, ECA-SOx).
Bunkering port details: the port at which compliant fuel was sought, the planned and actual bunkering dates, the quantity and grade of compliant fuel required.
Documentary evidence of non-availability: a list of bunker suppliers contacted (name, date, response), documentary attachments (emails, broker confirmations, port authority statements, supplier written responses or refusals). The Circ.878 form has a specific column for “supplier name,” “date contacted,” “date of response,” and “reason for non-availability.”
Current fuel oil situation: the current fuel oil in use (type, sulphur content as shown on the BDN), the quantity, the expected consumption rate, the ports where the non-compliant fuel will be burned.
Mitigation measures considered: whether a route deviation to an alternative bunker port was considered and why it was or was not practical, slow steaming, lay-time at anchorage to await a compliant delivery.
Master’s declaration and signature: the master certifies the information is accurate and complete.
The form is submitted to the flag state administration as soon as practicable, and a copy is provided to the competent authority of the next port of call where the relevant sulphur limit applies.
What a FONAR is not
The FONAR’s legal character is the source of the most persistent errors made by owners and masters:
A FONAR is not an exemption from MARPOL Annex VI. Regulation 18.2 does not say the ship is exempt from Regulation 14 during the period covered by the FONAR. It says the ship must document the non-availability and report it. The flag state and port state then decide what to do.
A FONAR is not a waiver. An accepted FONAR means the administration has decided, given the evidence, not to prosecute or detain the vessel for that specific instance of non-compliance. It does not create a precedent that applies to future voyages, future ports, or future inspections by different PSC regimes.
A FONAR is not a substitute for genuine commercial effort. MEPC.1/Circ.878’s documentation requirements reflect the IMO’s intention that the FONAR mechanism be used only where the non-availability is real and demonstrable. A FONAR supported by three email inquiries sent on the morning of departure to suppliers known not to stock compliant fuel will not survive scrutiny. A FONAR supported by documented inquiries to every listed bunker supplier in the port, a broker search of the regional market, and a port authority statement confirming stock-out at that port has a defensible evidentiary basis.
A FONAR does not protect the ship from the carriage ban under Regulation 14.1.3. If the ship is carrying non-compliant fuel without a scrubber, the carriage ban may apply regardless of the FONAR. The carriage ban and the sulphur limit are two legally distinct prohibitions. MEPC.1/Circ.880 addresses this point directly: it notes that where a ship has a FONAR and is carrying non-compliant fuel into a port, PSC authorities should consider de-bunkering of the non-compliant fuel as a condition of departure, alongside any penalty for the carriage-ban violation. The PSC inspector has discretion; the FONAR informs that discretion but does not bind it.
The de-bunkering consideration
MEPC.1/Circ.880 (Guidance for port State control on contingency measures for addressing non-compliant fuel oil, issued 2019) explicitly identifies de-bunkering as an option. A port state may require a vessel to remove all non-compliant fuel before departure, rather than simply accept the FONAR and allow the vessel to proceed. De-bunkering is operationally expensive and time-consuming: arranging a slop barge, pumping out service tanks, disposing of or transferring the non-compliant fuel. For a vessel already under a tight schedule, de-bunkering ordered by a PSC authority is a significant commercial penalty even before any fine is imposed.
The decision on whether to require de-bunkering versus accepting the FONAR as a basis for allowing the vessel to proceed to the next compliant bunkering port is a matter of port-state discretion. Factors that PSC inspectors weigh include: the sulphur content of the fuel relative to the applicable limit (a fuel at 0.52% used under a FONAR claiming global-cap non-availability is different from a fuel at 3.50% in a North Sea ECA vessel), the quality of the FONAR documentation, whether the flag state has formally accepted the FONAR, the vessel’s PSC detention history, and the distance and voyage plan to the next port where compliant fuel is available.
What counts as “genuine non-availability”
The FONAR mechanism rests on the concept that fuel oil non-availability must be genuine and documented. IMO guidance and flag state practice have settled on a working standard that requires:
Market-wide stock-out, not supplier preference. A ship that contacts only one supplier and finds that supplier is out of stock doesn’t have a FONAR case if other suppliers in the same port have compliant fuel. The ship must demonstrate it contacted all reasonable commercial sources in the port. A FONAR where the “unavailability” is that compliant fuel was available but at a price the owner found unacceptable will be rejected.
Documented supplier inquiry. Written evidence (email chains, broker logs, supplier written responses) is expected. A FONAR supported only by the master’s statement that “compliant fuel was not available” without any documentary support of the inquiry process is inadequate.
Reasonable alternative port consideration. The FONAR should address whether deviating to an alternative bunker port where compliant fuel was available was considered, and if not, why not (voyage economics, safety constraints, charter instructions, transit time). A vessel that bypassed a port with compliant fuel in favour of a port without, and then filed a FONAR, faces obvious questions.
Early notification. The Reg 18.2 obligation arises as soon as it becomes clear that compliant fuel won’t be obtained. Filing a FONAR after a PSC inspection has already begun is not the same as proactive filing before arrival at the port where the sulphur limit applies. Flag states and PSC authorities treat proactively filed FONARs materially more favourably than retrospectively filed ones.
Quantity reasonableness. The FONAR documents the quantity of non-compliant fuel expected to be consumed. A vessel carrying 2,000 metric tonnes of non-compliant residual fuel that files a FONAR claiming it could not obtain 20 tonnes of compliant fuel for an ECA passage draws scrutiny: why was a month’s worth of non-compliant fuel bunkered if a compliant passage was planned?
PSC discretion and flag state role
MARPOL is enforced through a dual-track system. The flag state is the primary enforcement authority for a vessel flying its flag. The port state controls the vessel while it is in port, and can inspect, detain, or expel it. The FONAR is submitted to both, and both can accept or reject it independently.
Flag states differ in their FONAR review procedures. Flags with large open registries and professional maritime administrations (Bahamas, Marshall Islands, Liberia, Panama, Cyprus, Malta) have established FONAR intake procedures and typically respond to a FONAR within 24 to 48 hours with a formal acknowledgement or a request for additional documentation. Some flag states accept the FONAR and issue a formal “noted” letter that the master can show to a PSC inspector as evidence the flag has been notified. That letter doesn’t bind the PSC inspector, but it is evidence that the regulatory notification obligation was fulfilled.
PSC authorities under the Paris MoU and Tokyo MoU apply MEPC.1/Circ.880’s guidance. That Circular recommends that PSC inspectors check whether the FONAR documentation demonstrates: (a) genuine non-availability at the last bunkering port, (b) notification to the flag state, (c) notification to the port of destination, and (d) a plan to bunker compliant fuel at the earliest opportunity. PSC inspectors also consider whether the vessel’s fuel oil record book and BDN history are consistent with the FONAR story.
FONAR frequency and the post-2020 supply picture
During the six months before and after 1 January 2020, global VLSFO supply chains were under pressure. Refiners had reconfigured but availability was patchy, particularly in smaller ports and for specific grades. Flag states reported elevated FONAR volumes during this period. The IMO does not publish a global FONAR count; flag states report individually to MEPC sessions. By 2022, major flag registries were reporting that FONAR submissions had fallen substantially from the 2019 to 2020 transition peak, as global VLSFO supply became routine at most significant bunker ports.
The Mediterranean ECA, which entered force 1 May 2025 under MEPC.361(79), is the most recent sulphur compliance expansion. Ports in the Mediterranean that previously supplied 0.50%-compliant fuel now need to supply 0.10%-compliant fuel (ECA-grade LSMGO or ULSFO) to vessels entering the Mediterranean ECA boundary, or vessels must have completed the switch before entry. FONAR submissions attributable to Mediterranean ECA non-availability are an expected operational reality during the initial years of that ECA’s operation, as supply chains adjust.
BDN and FONAR in the broader compliance chain
The BDN as the source document for emissions reporting
The BDN’s sulphur content and quantity data feed into every fuel-consumption-based compliance regime operating on the vessel, not just MARPOL Annex VI Regulation 14. The EU MRV Regulation, the IMO DCS (Data Collection System), the EU ETS for shipping, and the CII rating system under MARPOL Annex VI Regulations 22A-22C all draw on BDN-derived fuel consumption data as their primary input. The SEEMP Part III annual fuel consumption reporting requires BDN-consistent data across the full year.
An error in a BDN, whether a misstatement of sulphur content, density, or quantity, propagates into all of those downstream calculations. A vessel that discovers a systematic error in its BDN data, such as a supplier who consistently overstated fuel density, may need to correct not only its MARPOL compliance records but also its EU MRV submissions for the relevant reporting year.
Where FONAR does not help
The FONAR is a sulphur-cap instrument. It has no analogue in the GHG intensity frameworks that apply to shipping from 2025 onward.
FuelEU Maritime, which entered into force from 1 January 2025 for EU voyages, sets a greenhouse gas intensity limit (grams of CO2 equivalent per megajoule of energy) on a well-to-wake basis. There is no provision in FuelEU for a “GHG fuel non-availability report.” A vessel that can’t obtain low-GHG fuel remains subject to the FuelEU intensity calculation; it must either pool with a compliant vessel, bank surplus from another year, or pay the FuelEU penalty. Non-availability of low-carbon fuel is a commercial and planning risk, not a regulatory defence.
The IMO Net-Zero Framework, adopted at MEPC 83 in April 2025, operates on similar principles at the global level from 2027. Again, no non-availability defence is built into the framework.
This asymmetry creates a real planning problem for owners operating in regions where low-GHG fuels are not commercially available. FONAR protects against sulphur non-compliance. It does not protect against GHG intensity non-compliance.
The charterer dimension
Under a time charter, the charterer typically supplies the fuel. The BDN evidences what the charterer put aboard and at what declared sulphur content. If a PSC inspector finds the fuel non-compliant and the BDN states compliant values, the dispute between owner and charterer about who is liable for the non-compliance cost turns partly on whether the BDN was accurate and whether the MARPOL-delivered sample is available to test.
BIMCO’s Bunker Clauses 2024 for charter parties address BDN data integrity obligations between the owner and charterer. The clauses allocate responsibility for obtaining accurate BDNs and for the costs of off-spec deliveries, but they cannot override the PSC inspector’s authority to detain the vessel regardless of what the charter party says about who is at fault.
Comparison: BDN versus FONAR
| Feature | BDN | FONAR |
|---|---|---|
| Regulatory basis | MARPOL Annex VI Reg 18.5 | MARPOL Annex VI Reg 18.2 |
| Who prepares it | Bunker supplier | Master of the vessel |
| When prepared | At each bunker delivery | When compliant fuel could not be obtained |
| Retained on board | 3 years from delivery | No mandatory on-board retention period, but copies should be kept |
| Filed with | Not filed; provided to vessel and available for inspection | Flag state administration and port authority at next port of call |
| Legal character | Record of what was delivered and declared | Documentary defence for non-compliance |
| Grants exemption from Reg 14 | No | No |
| Admissible in PSC detention proceedings | Yes; primary evidence of fuel source and declared sulphur | Yes; evidence of procedure compliance; does not bind PSC inspector |
| IMO standardised format | MEPC.1/Circ.792 (BDN format) | MEPC.1/Circ.878 (FONAR format) |
| Companion physical evidence | MARPOL-delivered sealed sample | Documented supplier inquiry evidence |
Practical vessel-side procedures
BDN management on board
A vessel’s chief engineer is responsible for receiving the BDN before or at the time the bunker transfer is completed. The key procedural steps that determine whether the BDN will withstand a PSC inspection are:
Check the BDN fields against the mandatory content list in Reg 18.5 before signing. The BDN must carry the supplier’s name and address, the receiving vessel’s name and IMO number, the port and date of delivery, the product name and grade, the quantity in metric tonnes, the density at 15 degrees C, the sulphur content in % m/m, the flash point, and the Regulation 14 and 18.3 compliance declaration. A BDN missing any of these fields is deficient on its face.
The declared sulphur content must be at or below 0.50% m/m for global-cap compliance, or at or below 0.10% m/m for ECA-grade fuel. Any BDN that declares a value above the applicable limit should not be accepted without an immediate FONAR procedure being triggered.
The MARPOL-delivered sample must be drawn from the ship’s manifold throughout the entire bunker transfer using a properly installed continuous-flow drip sampler. Sampling only at the start and end of transfer is not compliant with MEPC.182(59). The sample must be sealed in the presence of both the ship’s officer and the supplier representative before the barge or truck departs. Seal numbers are recorded on the BDN. The sample is labelled with the vessel name, IMO number, bunker port, date, product name, and BDN number.
BDNs are filed chronologically in a dedicated BDN folder accessible to the master and chief engineer. All BDNs from the past three years must be present. The fuel oil record book entries must cross-reference BDN numbers for every transfer.
FONAR preparation and notification timing
The FONAR procedure should begin as soon as the master determines that compliant fuel cannot be obtained at the planned bunkering port. This means the inquiry process, and the documentation of it, should start well before the vessel berths for bunkering, not after the bunkering vessel has departed with only non-compliant fuel delivered.
Best practice, reflected in flag state FONAR guidance from Bahamas Maritime Authority, Marshall Islands Maritime Administrator (MIMDAS), and Liberia (LISCR), is to:
Contact all bunker suppliers listed in the port’s commercial bunker directory, not just the vessel’s preferred supplier. Send written inquiries. Record the date, the recipient, and the response or non-response.
Contact the port authority to request confirmation that compliant fuel is not available at that port on those dates. A port authority statement is strong corroborating evidence.
Contact the company’s bunker broker to document a market search beyond the specific port.
Consider whether a route deviation to a port with confirmed compliant fuel availability is possible and document the voyage economics and safety constraints that prevent it if it is not.
Notify the flag state by the vessel’s most reliable means, retaining proof of transmission. Send the FONAR to the port authority at the next port of call where the sulphur limit will apply, ideally before arrival.
Retain all documentation on board: the FONAR form completed per MEPC.1/Circ.878, all supplier inquiry correspondence, the flag state notification and any response, the port authority notification.
Company management system integration
The ISM Code requires shipowners to establish a documented safety management system. FONAR procedures and BDN management should be integrated into the company’s ISM-compliant SMS (Safety Management System). A vessel whose crew are not trained in the FONAR procedure, or whose SMS has no protocol for FONAR situations, is in a weaker position before a flag state investigation or PSC detention appeal.
The ISM Code (International Safety Management Code, SOLAS Chapter IX) requires companies to identify non-conformities in their operations and address them. A PSC detention for sulphur non-compliance where the vessel had no FONAR procedure documented in its SMS is likely to generate a major non-conformity in the company’s next ISM audit.
Limitations
This article addresses FONAR and BDN documentation as they apply under MARPOL Annex VI Regulation 14 (sulphur limits) and Regulation 18 (documentation). Several important limitations apply:
The FONAR is a defence of last resort, not a compliance strategy. Owners who treat the FONAR as a routine planning tool rather than an exceptional emergency procedure invite escalating PSC scrutiny, flag state intervention, and the risk that repeated FONARs are rejected on the ground that the owner has not taken adequate steps to ensure compliant fuel availability.
Test tolerance thresholds are version-specific. MEPC.1/Circ.864’s thresholds of 0.53% and 0.11% were established for the current analytical methods. If ISO 14596 or ASTM D4294 test protocols change materially, the thresholds may be revised. PSC authorities use the current Circular in force at the time of inspection.
Flag state and PSC discretion is real and variable. This article describes the IMO guidance framework. Individual flag states and PSC MoU regions apply that guidance with varying degrees of strictness and procedural rigour. A FONAR that would be accepted by one flag state may be rejected by another. The Paris MoU’s published detention statistics show that EU-adjacent flag states face higher PSC scrutiny than open registries with fewer EU port calls.
The carriage ban and the sulphur limit are separate violations. A vessel operating under a valid FONAR may still be in violation of the carriage ban under Regulation 14.1.3 if it is carrying non-compliant fuel without a scrubber. The FONAR does not provide a carriage-ban defence.
MEPC.1/Circ.878 is guidance, not binding regulation. The standard FONAR format is recommended but not legally mandatory under MARPOL. However, a FONAR not following the standard format will receive less favourable treatment from port state and flag state authorities that expect it, and some port states have published guidance stating that FONARs not in the standard format will not be processed.
BDN data accuracy depends on supplier integrity. The BDN is a supplier declaration. It is not independently verified at the point of supply. Systematic supplier mis-declaration of sulphur content (whether accidental or deliberate) is the root cause of many bunker quality disputes. The MARPOL-delivered sample is the mechanism for detecting and proving such mis-declaration, but only if it is correctly drawn and retained.
This article does not address GHG intensity compliance. FuelEU Maritime and the IMO Net-Zero Framework create separate documentary obligations for WtW intensity that are additive to, and not substitutable for, the MARPOL Annex VI BDN and FONAR regime. Those frameworks are addressed in the FuelEU Maritime and IMO Net-Zero Framework articles.
Related calculators
The FONAR sulphur compliance calculator lets operators check whether a FONAR situation is likely to arise given a vessel’s voyage plan, current fuel inventory, and the applicable sulphur limit at the destination ECA or port. The bunker quality dispute variance calculator assists in assessing whether a BDN-declared sulphur value and an in-use or onboard sample test result are within the MEPC.1/Circ.864 test tolerance thresholds for the 0.50% and 0.10% limits. The MARPOL fuel oil sampling calculator covers the sample volume and drip-sampler flow-rate parameters for Reg 18 sampling compliance. The BDN and ROB reconciliation calculator reconciles bunker delivery notes with remaining-on-board figures across a voyage.