Better watch your ‘back-to-back’: Understanding Back-to-Back Charterparties: Key Risks and Considerations for Members in Marine Insurance P&I Club News 06/01/2026 In today’s complex chartering landscape, it is common for vessels to be fixed under a chain of charterparties, often with a head owner, a charterer in the middle, and a sub-charterer. These arrangements are frequently described as “back-to-back”, implying that the terms across the contracts align seamlessly. But in practice, “back-to-back” is often more assumption than reality. This article explores what “back-to-back” really means in practice, highlights common gaps, and offers guidance on how Members can protect their position. What is a Back-to-Back Charterparty? A back-to-back charterparty typically refers to a situation where a party (usually an intermediate charterer) enters into two contracts: one as charterer (under the head charter) and one as owner (under the sub-charter), with the intention that the terms and obligations mirror each other. This structure aims to pass liabilities and obligations seamlessly down the chain. However, unless terms are carefully aligned, even minor inconsistencies can cause serious gaps in protection, turning the middle party into an unintended buffer between conflicting obligations. For the purposes of this article, the term back-to-back refers primarily to scenarios where both the head and sub-charters are time charterparties. While a voyage charterparty may include clauses that reflect provisions in a time charterparty up the chain, it cannot, by its nature, be truly back-to-back. Under a voyage charter, the owner bears the voyage risks and earns freight for carrying a specific cargo, while under a time charter, the charterer controls the vessel’s employment and bears operational costs and delays. Therefore, while a voyage charter may be drafted on similar terms with a time charter, it cannot be made fully back-to-back because the allocation of risk, responsibility, and cost differs between the two forms. Nevertheless, references to voyage charterparties are included below where relevant, in order to illustrate the risks Members may face when they are in the middle of a contractual chain. Key Risks and Mismatched Clauses Port/Berth Safety Warranties Safe port/berth warranties are typically found in time charterparties but may be differently worded (such as one requiring due diligence vs one imposing strict liability) or may be absent. If a head charterparty includes a warranty and the sub-charterparty does not, the charterer in the middle may be left liable for unsafe port claims with no contractual recourse. In addition, where there is no express term as to safety it seems that the court may take different approaches in implying a term as to safety depending on the specific circumstances. In the context of a voyage sub-charterparty for example, where the voyage is between specifically identified ports and no express safe port warranty is included, it is unlikely that such warranty making the charterers responsible for the safety of the port is implied. Because the owner will have been given the opportunity to consider the safety of the stipulated ports. Similarly, where a voyage charterparty identifies, a number of possible loading or discharging ports from which the charterer i can nominate the operative port, a safe port/berth warranty will not automatically be implied in the absence of an express undertaking. Any such implied warra