Joint Ownership Agreement UK: Cars, Boats & Aircraft

At a glance

• What it is: a private contract between two or more people who together own a car, boat, aircraft or similar high-value chattel, recording ownership shares, costs, usage and what happens on exit.
• Not for houses or land. Buying a property jointly is governed by property law, not this kind of agreement — see joint tenants vs tenants in common and declarations of trust instead.
• Registration is not the same as ownership. GOV.UK confirms the DVLA V5C is "not proof of ownership" — it only shows the registered keeper.
• Boats can reflect joint ownership on registration. GOV.UK confirms that if you own a boat with other people, every owner needs their own account before you register it on the UK Ship Register.
• Aircraft registration can record co-owners directly. Under the Air Navigation Order 2016, the CAA's register can list every person entitled to a legal or beneficial share in a UK-registered aircraft.
• Core terms to cover: ownership shares and contributions, usage and decision-making, costs and insurance, liability, and what happens if someone wants out, dies, or a dispute arises.
• If you can't agree: GOV.UK's free small claims mediation service and, as a last resort, a county court money claim are both available to resolve disputes over shared assets.

What a joint ownership agreement is

A joint ownership agreement is a private contract between two or more people who together own a physical asset, most commonly a vehicle, boat or light aircraft. It sits alongside the legal title to the asset and records the commercial arrangement the owners have agreed between themselves, separately from whatever official register applies.

The document usually names each owner, sets out their percentage share, and explains how costs, use and decisions will be handled day to day. It also deals with the less pleasant scenarios: one owner wanting to sell up, a dispute about usage, damage or write-off, the death or bankruptcy of a co-owner, and how disagreements get resolved.

Done properly, it is a short, practical document that prevents most of the arguments people have after the fact, precisely because it answers the questions before they become urgent.

A house, flat or piece of land is different territory entirely. Property is co-owned as either joint tenants or tenants in common, a choice recorded with HM Land Registry rather than in a private agreement, and disputes between property co-owners are resolved under the Trusts of Land and Appointment of Trustees Act 1996, not through a document like the one described here. If that's what brought you here, our guides on joint property ownership and tenants in common and on using a declaration of trust for a jointly owned property cover it in full. The rest of this page is about cars, boats and aircraft.

Why registration records aren't proof of ownership

Every category of asset covered here has an official register, and every one of those registers works differently. Understanding the difference matters, because assuming a register settles ownership is the single most common mistake co-owners make.

Cars: the V5C and the registered keeper

The V5C, commonly called the log book, records the registered keeper of a vehicle: the person responsible for taxing it, registering changes, and receiving correspondence from DVLA. GOV.UK has been explicit about this since the V5C was redesigned: buyers often mistakenly believe the V5C is proof of ownership, and "this is not the case." Only one person can be named as keeper, even if two or more people actually own the car. If you are buying jointly, agree who will be the named keeper for administrative purposes, and record in your joint ownership agreement that being the keeper does not mean sole ownership.

Boats: the UK Ship Register

Boats used at sea are registered with the UK Ship Register, which has four parts depending on how the boat is used. Part 1 suits commercial or pleasure vessels where the owner wants a marine mortgage or plans to spend more than six months outside the UK. Part 3, the Small Ships Register, suits smaller pleasure vessels under 24 metres and mainly proves the boat's nationality when sailing abroad. Usefully for joint owners, GOV.UK confirms that if you own the boat with other people, all owners need their own account before you can register it online, so a shared boat's registration can reflect joint ownership more directly than a car's V5C can. Registration fees are payable and reviewed periodically, so check the current fee on GOV.UK before applying.

Aircraft: the CAA register

Aircraft flown in the UK must be registered with the Civil Aviation Authority, which maintains the UK Register of Civil Aircraft. Under the Air Navigation Order 2016, an application for registration must include information about the aircraft's ownership, and the CAA must record the name and address of every person entitled as owner to a legal interest in the aircraft, including a share of the aircraft. Anyone who becomes the owner of a UK-registered aircraft must inform the CAA in writing within 28 days. This means the aircraft register can reflect co-ownership more precisely than a car's log book, but it remains an administrative and safety record, not a substitute for a written agreement covering running costs, usage and what happens if a co-owner wants to leave.

What to include in your agreement

Ownership shares and contributions

State each owner's percentage share and how it was calculated, whether by equal split, by contribution to the purchase price, or by some other agreed formula. Record how future capital contributions (a major repair, an upgrade, a new engine) affect those shares, if at all.

Usage, decisions and day-to-day costs

Spell out how bookings or usage slots work, how routine costs like fuel, mooring, hangarage, servicing and MOTs are paid (a joint account often helps), and what spending threshold requires unanimous agreement rather than one owner acting alone. For boats and aircraft, also cover who organises annual inspections, safety certification and insurance renewals.

Insurance and liability

Confirm who arranges insurance, whether it is held jointly or by one named policyholder, and how a claim is handled if the asset is damaged or written off. Decide in advance who pays an excess, whether an at-fault co-owner compensates the others for lost use, and how any payout is divided if the asset is a total loss.

Exit, death and bankruptcy

This is the most important part of the agreement. Include a right of first refusal for the remaining owners if someone wants to sell their share, a valuation method, a sensible notice period, and clear provisions for what happens on death or bankruptcy so a stranger or an unwilling beneficiary cannot become your co-owner by default. If you are thinking further ahead about how a share in a valuable asset should pass to family over time, a discretionary trust is a separate structure worth understanding, though it is a bigger step than most joint ownership arrangements need.

Buying jointly with a partner or family member

Buying a car, boat or aircraft with a partner you live with but are not married to raises the same questions as buying it with a friend or business associate, plus one more: how does this purchase fit into your wider finances? A joint ownership agreement for a single asset is not a substitute for a broader cohabitation agreement covering your home, savings and other shared property. If you already have a cohabitation agreement, make sure it is consistent with, or expressly refers to, any separate joint ownership agreement for a specific asset, so the two documents do not contradict each other. If the shared purchase in question is actually the home itself, use the property-specific guides linked above instead, this agreement is not the right document for that.

If you disagree: mediation and court options

Even a well-drafted agreement can leave a gap, and some co-owners never wrote anything down at all. If a disagreement can't be resolved directly, GOV.UK's small claims mediation service is free and can help resolve disputes over money or shared goods without a court hearing, usually more quickly and cheaply than litigation. If mediation doesn't work or isn't suitable, a co-owner can make a county court claim for money owed or to resolve the dispute; GOV.UK's guidance on making a court claim for money sets out how to apply, the fees involved, and what happens after a claim is made. Building a dispute-resolution clause, pointing to mediation before court, into your agreement from the outset usually keeps costs and stress far lower than reaching for either option cold.

How to put the agreement in place

1. Agree the basics before drafting anything. Sit down with your co-owners and talk through ownership shares, how much each of you is contributing, who uses the asset and when, and how ongoing costs like insurance, fuel, mooring, hangarage and servicing will be split. Getting this aligned in conversation first saves hours of redrafting later and surfaces mismatched expectations early.
2. Record who is the registered keeper or holder. For a car, only one name goes on the V5C with DVLA, and that person is responsible for tax, SORN and receiving penalty notices. For a boat or aircraft, work out whether your registration can name every co-owner directly and, if so, make sure it does. Your agreement should state clearly that being the named keeper or holder is administrative, not a transfer of ownership.
3. Set out usage, costs and decision-making. Spell out how bookings or usage slots work, how routine costs are paid, what happens with unexpected repairs, and what spending threshold requires unanimous agreement.
4. Deal with exit, death and disputes. Include a right of first refusal for the other owners, a valuation method, a sensible notice period, and what happens on death or bankruptcy. Add a simple dispute clause pointing to mediation before court.
5. Register or update the relevant record. Complete or update the DVLA, UK Ship Register or CAA registration as applicable, keeping a copy of whatever confirmation you receive with your agreement.
6. Sign, date and store copies. Each owner should sign the agreement, ideally with a witness, and keep their own copy. Store a copy with the vehicle, vessel or aircraft paperwork and consider lodging one with a trusted third party. Review the agreement if circumstances change, for instance if a new co-owner joins or the asset is significantly upgraded.

This guide provides general information about joint ownership agreements for cars, boats and aircraft in England and Wales. It is not legal advice and is not a substitute for advice tailored to your specific circumstances. The law and guidance described was accurate as at July 2026 and is subject to change, so always check GOV.UK and legislation.gov.uk for the most current position, including current registration fees.

Last reviewed: July 2026 by a non-practising solicitor · Next review due: July 2027 or on legislative change.