When two or more dentists decide to work from the same premises, they face an early and consequential choice about how to structure the relationship. Do they remain separate businesses that simply share the cost of the building and the staff, or do they merge into a single business and share the profit? These are two very different arrangements, an expense-sharing arrangement on one hand and a full partnership on the other, and they carry quite different consequences for tax, liability, VAT and the NHS contract.

The distinction is often blurred in conversation, with dentists describing themselves as in partnership when in substance they only share costs, or sliding into a partnership without meaning to. This guide draws the line clearly and compares the two structures across the points that matter, so you can choose deliberately rather than by accident. The figures are illustrative and the position is for 2026/27.

What an expense-sharing arrangement is

An expense-sharing arrangement is exactly what it sounds like. Several dentists work from the same premises and share the running costs, rent, staff wages, equipment, utilities and so on, but each keeps their own income and is taxed on their own profit. They are not in business together. Each dentist is a separate sole trader, or a separate limited company, and the only thing they share is the cost base, apportioned between them under an agreed formula such as by surgery, by sessions or by headcount.

The mental model is a cost-sharing club. The shared costs are pooled and split, but the income stays with whoever earned it. A strong-performing dentist keeps the benefit of their own productivity, and a quieter dentist bears their own lower income, because their profits are never combined.

What a partnership is

A partnership is a single business carried on by the partners together. All the partners' practice income is pooled into one partnership profit, which is then shared between them under the profit-sharing arrangement and taxed in their hands. The partnership is tax-transparent, so the firm itself does not pay income tax, and instead each partner is taxed on their share of the firm's profit under section 850 of the Income Tax (Trading and Other Income) Act 2005. The partners share the rewards of the whole practice, and they share its risks and liabilities too.

A partnership can be a traditional general partnership or a limited liability partnership, the latter giving limited liability while still being taxed as a partnership. Our guides to partnership capital accounts and profit-sharing and to financing a partnership buy-in cover the mechanics of how a partnership actually runs.

The core difference: shared costs only versus shared profit

Everything else follows from one distinction. In expense-sharing, the dentists share costs only and keep their income separate. In a partnership, the dentists share profit, which means they pool both income and costs into one figure and divide the result. That single difference drives the tax, the liability, the VAT and the NHS-contract position, so it is the question to settle first.

Tax: separate sole traders versus a profit allocation

In an expense-sharing arrangement, each dentist is taxed as a separate business. Each prepares their own accounts, claims their own apportioned share of the shared costs as expenses, and is taxed on their own profit through Self Assessment at the combined self-employed marginal rates. There is no pooling, so one dentist's good or bad year does not change another's tax.

In a partnership, there is one profit figure, allocated to the partners under the profit-sharing arrangement, and each partner is taxed on their allocated share under section 850. The partnership files a partnership return, and each partner reports their share on their own return. The pooling means risk and reward are shared, so a partner's taxable income depends on the whole practice, not just their own chair.

How shared costs are apportioned in expense-sharing

The mechanics of an expense-sharing arrangement turn on the apportionment formula, and getting it fair and clear is the practical heart of the arrangement. The shared costs, rent, reception and nursing staff, utilities, materials held in common, are pooled and divided between the dentists under an agreed basis. Common bases are:

  • By surgery, where each dentist pays for the rooms they use.
  • By sessions, reflecting how much time each dentist works from the premises.
  • By headcount or an equal split, the simplest but not always the fairest.
  • By usage, for variable costs such as materials or lab work, charged to whoever incurs them.

Each dentist then claims their apportioned share of the shared costs as an allowable expense of their own business, against their own income. Because the dentists are separate businesses, the apportionment has to be genuine and documented, and the recharges between them need to be handled consistently so that everyone's accounts reflect the same numbers. A vague or shifting apportionment is a frequent source of friction, so the formula belongs in the written agreement.

Employing shared staff in expense-sharing

Shared staff are where expense-sharing most often goes wrong in practice. A receptionist or nurse who works for all the dentists has to be employed by someone, and the usual options are that one dentist employs them and recharges a share to the others, or that a jointly owned vehicle employs them. Either way, the employer National Insurance, the payroll, the auto-enrolment pension obligations and the recharge arrangements all have to be set up correctly and documented. If one dentist is the employer, they carry the employer obligations and recover a share through the recharge. Getting this wrong, by leaving the employment relationship unclear or the recharges inconsistent, creates both employment-law and tax problems, so the staffing structure deserves as much care as the cost split. Our guides to how dentists are taxed and to employing staff are useful background here.

Liability: own risk versus joint and several

This is often the deciding factor. In expense-sharing, because each dentist is a separate business, one dentist is not normally liable for another's business or professional debts merely because they share premises. The exposure to each other is limited.

In a general partnership, the partners are jointly and severally liable for the partnership's debts and obligations, which means each partner can be pursued for the whole. A limited liability partnership mitigates this, giving the members limited liability for the LLP's debts, which is one reason many dental partnerships choose the LLP form. For dentists who value keeping their exposure to colleagues low, expense-sharing or an LLP is more comfortable than a general partnership.

VAT and registration: per-dentist versus one taxable person

VAT registration is tested per taxable person. In expense-sharing, each dentist is a separate person, so each tests their own taxable, non-exempt turnover against the ninety thousand pound registration threshold. Most dental care is exempt from VAT, so this only bites where a dentist does enough standard-rated work, typically cosmetic treatment, to approach the threshold on their own.

In a partnership, the firm is a single taxable person, so the partnership's combined taxable turnover is tested as one figure. A group doing a meaningful volume of cosmetic work could find that, pooled in a partnership, the combined taxable turnover crosses the threshold, whereas split across separate expense-sharing dentists it might not. The interaction with the dental VAT exemption is set out in our wider VAT material, and the structure choice can change who, if anyone, has to register.

NHS contract and who holds it

In expense-sharing, each dentist holds their own NHS contract arrangement in their own name, because they are separate businesses. In a partnership, the NHS contract is usually held by the partnership. This matters a great deal, because the NHS contract is frequently the most valuable thing a dentist owns, and its continuity and value depend on who holds it and what happens on a change. Settle the NHS-contract position early with the commissioner, because it can be the practical constraint that decides the structure.

When expense-sharing suits a group

Expense-sharing tends to suit dentists who want to stay independent while sharing overheads. It fits well where:

  • The dentists want to keep their own income and not subsidise each other.
  • They value low liability exposure to colleagues.
  • They each want to hold their own NHS contract.
  • They want the freedom to leave or change without unwinding a shared business.

It is the lighter-touch arrangement, and many groups of dentists run perfectly well this way for years.

When a full partnership suits

A partnership suits dentists who genuinely want to build one business together. It fits where:

  • The dentists want to share profit, risk and reward as a single firm.
  • They want to grow and invest jointly, and plan a shared future and exit.
  • They are comfortable with the closer financial ties and, in a general partnership, the joint liability.

A partnership is the natural structure for partners who see themselves as co-owners of one practice rather than independent dentists under one roof. Our guides to sole trader versus limited company and to whether incorporation is still worth it are worth reading alongside, because some growing partnerships also weigh up incorporating.

The accidental partnership: a real risk

One of the biggest dangers in expense-sharing is drifting into a partnership without meaning to. A partnership can exist in substance even without a formal agreement, if the dentists actually carry on a business together and share profit. Expense-sharing dentists who start pooling income, sharing the upside of a good month, running joint marketing under a single brand and presenting themselves to the world as one practice, can find that they have created a partnership in law, with all the joint and several liability that brings, and possibly without realising it.

The consequences are serious. An accidental partnership can mean one dentist becomes liable for another's business debts, the income tax position changes, and the NHS contract and VAT analysis shift. The protection against this is twofold: a clear written expense-sharing agreement stating that the dentists share costs only, keep separate income and do not intend to be partners, and behaviour that matches, keeping income separate, invoicing in their own names and not holding out as a single firm. The agreement on its own is not enough if the conduct says otherwise, because substance governs.

What each structure means for selling or leaving

The structures also differ when a dentist wants to exit or sell. In expense-sharing, each dentist owns their own practice, their own patient list and their own NHS contract, so they can sell or wind down their own business with relatively little entanglement, subject to the premises arrangement and any notice to the others. In a partnership, a leaving partner has to be bought out of their share of the joint business, which is the buy-out process covered in our guide to buying out a retiring partner, and an incoming partner buys in, as in our guide to financing a buy-in. The partnership ties the dentists' exits together far more than expense-sharing does, which is a benefit if they want a shared, planned future and a constraint if they value independence.

Switching from one to the other

Groups sometimes start with expense-sharing and move to a partnership as the relationship deepens, or occasionally the reverse. Moving from expense-sharing to a partnership means combining separate businesses into one, which involves pooling income, agreeing a profit-sharing ratio and dealing with goodwill, and that combination can have capital gains and other consequences. It is not just a paperwork change, so it should be planned with advice. The reverse, splitting a partnership into separate practices, is more involved still.

A worked illustration

Take three dentists who share a building and a nurse. As an expense-sharing group, each is a separate sole trader, each is taxed only on their own profit after their apportioned share of the rent, the nurse and the other shared costs, and each holds their own NHS contract. A strong year for one of them does not raise the others' tax. As a partnership, the three pool their income into one profit, share it under an agreed ratio, are each taxed on their share under section 850, hold the NHS contract through the firm, and are jointly liable for the practice's debts unless they use an LLP. The same three dentists in the same building have a materially different tax, liability and contract footprint depending only on which structure they chose.

Getting the documentation right

Whichever structure suits, the documentation is what makes it work. An expense-sharing arrangement needs a written agreement that sets out how costs are apportioned, how shared staff and equipment are handled, what happens when a dentist leaves, and, importantly, that the dentists are not in partnership and do not share profit. Without that clarity, dentists can drift into an accidental partnership, with all the joint liability that brings, simply by behaving like partners. A partnership needs a proper partnership agreement covering profit shares, capital, decision-making, the NHS contract and exit terms.

Before choosing, a specialist dental accountant should model how each structure taxes the dentists involved and how it affects VAT and the NHS contract, and a solicitor should draft the agreement. The two arrangements look superficially similar, several dentists under one roof, but they are fundamentally different in law and tax, and choosing deliberately is far cheaper than untangling the wrong choice later.