Section 24 and Joint Property Ownership: How Is Tax Split?

When two people own a rental property together, Section 24 does not simply halve the tax bill. Each owner reports their own share of the rent and the mortgage interest, and the mortgage interest restriction is then applied to each person separately. That separation is the whole game: it means the way income is split between joint owners, and the rate each of them pays, decides how much of the finance cost is actually relieved.

Get the split right and a higher rate owner can move income to a basic rate co-owner and keep more of the relief. Get it wrong, or assume spouses can pick any split they like, and HMRC reverts you to a default that may cost more tax than you expected. This guide sets out how Section 24 lands on joint ownership, the spouse 50/50 rule, when Form 17 genuinely helps, the declaration of trust that has to come first, the capital gains angle on moving a share, and what changes from April 2027.

How does Section 24 apply to joint property owners?

Section 24 of the Finance (No. 2) Act 2015 removed the deduction of residential finance costs from rental profit and replaced it with a basic rate tax reducer. The restriction has been fully in force since 6 April 2020. Mortgage interest, and other qualifying finance costs, no longer reduce taxable rental profit. Instead, the owner gets a tax credit worth 20% of the lower of their finance costs, their property profits, or their adjusted total income above the personal allowance.

For a single owner that is one calculation. For joint owners it is two (or more) separate calculations, because rental income from co-owned property is taxed on each individual on their share. Each owner enters their portion of the income, expenses and finance costs on their own return, and the 20% credit is worked out on their slice of the interest, capped by their own profits and income. The property produces one set of accounts, but the tax outcome is built person by person.

This is why two owners with identical shares can have very different effective relief. A basic rate owner would historically have relieved the interest at 20% as an expense, so the 20% credit broadly replaces what they had. A higher rate owner would have relieved it at 40% or 45%, so the flat 20% credit leaves them worse off. The restriction bites hardest where a higher rate owner holds the larger share of a heavily geared property.

The default split follows beneficial ownership

For owners who are not married or in a civil partnership, income and the matching finance costs are split by beneficial ownership, which usually mirrors the legal title. Own 60/40 on the deed, with no trust to say otherwise, and the rent, the deductible expenses and the interest credit are all shared 60/40. There is no facility for unmarried co-owners to elect a different split for tax. If the real beneficial interest differs from the title, that has to be documented with a genuine declaration of trust and evidence of who actually funded the purchase, and it has to be the real position, not a label applied for tax.

The spouse and civil partner 50/50 deeming rule

Spouses and civil partners are treated differently. Where they hold property in their joint names, ITA 2007 s.836 deems the income to be split 50/50, regardless of the underlying beneficial ownership. So even if one spouse beneficially owns 90% of the property, the default for tax is still half each. This catches a lot of couples out, because they assume the deed governs the split when in fact the statute overrides it.

The 50/50 deeming is the starting point, not a planning tool you opt into. To break out of it and report on the real beneficial shares, a couple uses a Form 17 election. The rest of the household planning around Section 24 turns on that one mechanism, so it is worth being precise about how it actually works.

Form 17: the election out of 50/50, not into a chosen split

Form 17 is the single most misunderstood part of joint ownership and Section 24. The common belief is that Form 17 lets a couple choose their split. It does not. Form 17 is the election out of the s.836 50/50 default and into the actual beneficial ownership split. If the real beneficial interests are 70/30, Form 17 produces a 70/30 income split. It cannot deliver 80/20, 90/10, or any figure that does not match the underlying ownership.

Three conditions all have to be met, and missing any one invalidates the election:

• Tenants in common, not joint tenants. Joint tenants own the whole undivided, with no separable share to declare, so they cannot use Form 17. The couple must hold as tenants in common in unequal shares.
• A contemporaneous declaration of trust. The unequal beneficial interests must already exist and be evidenced by a declaration of trust executed at or before the time the split changes. Form 17 reports the existing split to HMRC; it does not create it.
• Both signatures and the 60-day window. Both spouses sign, and the form must reach HMRC within 60 days of the later signature. A form that arrives late is invalid, and the 50/50 default simply re-applies.

Once accepted, the election covers all property the couple holds in those declared shares, not selected properties, and stays in force until a new declaration is made, the underlying beneficial interest changes, the couple stop living together, or one of them dies. For the full mechanics, filing detail and revocation, see our guide on the Form 17 declaration of beneficial interest and the supporting declaration of trust that has to underpin it.

Worked example: where Form 17 earns its keep

Take a couple who own a let property generating GBP30,000 of rent with GBP12,000 of mortgage interest. One spouse is a higher rate taxpayer, the other a basic rate taxpayer with spare basic rate band. They already hold as tenants in common in beneficial shares of 25% (higher rate spouse) and 75% (basic rate spouse), set out in a declaration of trust.

Position	Higher rate spouse	Basic rate spouse	Effect
Default 50/50 (no Form 17)	GBP15,000 income, GBP6,000 interest credit basis	GBP15,000 income, GBP6,000 interest credit basis	Half the rent taxed at higher rates; credit capped at 20%
Form 17 to real 25/75 shares	GBP7,500 income, GBP3,000 interest credit basis	GBP22,500 income, GBP9,000 interest credit basis	Higher rate income falls by GBP7,500; more profit taxed at basic rate

The election moves GBP7,500 of income off the higher rate spouse and onto the basic rate spouse, so it is taxed at 20% rather than 40%. Both still receive the 20% finance cost credit, but the household keeps more of the rental profit because less of it is exposed to higher rate tax. The saving comes from the rate differential, not from the credit, which is the same percentage for both.

Two cautions. First, the 25/75 beneficial split has to be real and documented before Form 17 is filed; the form declares it, it does not manufacture it. Second, if creating that split involves the basic rate spouse taking on a share of the mortgage debt, the debt assumed is chargeable consideration under FA 2003 Sch 4 para 8, and SDLT (or LTT in Wales, LBTT in Scotland) can be due even though no money changes hands. For couples wrestling with the underlying decision, our guide on the unequal rental income split for spouses compares the routes in detail, and civil partners get the same treatment, covered in civil partnerships and joint property ownership.

The capital gains angle: transferring a share to a spouse

Reshaping ownership to improve the Section 24 position usually means transferring a beneficial share, and that raises capital gains tax. The position depends entirely on who receives the share.

Transfers between spouses or civil partners who are living together happen on a no gain, no loss basis. No CGT arises on the transfer itself, and the receiving spouse takes on the transferor's original base cost and acquisition date. The gain is deferred, not wiped out: it surfaces when the property is eventually sold. That is what makes a pre-sale transfer to a spouse a genuine planning tool rather than a tax trigger. The detail is set out in our guide on CGT on transferring property to a spouse.

Transfers to anyone else are different. A move to an unmarried partner, an adult child or a friend is a disposal at market value, even with no money involved, because the parties are connected or the gift rule applies. That can crystallise a residential property gain taxed at 18% within the basic rate band and 24% above it, against an annual exempt amount of just GBP3,000 for 2026/27.

The flip side is that holding a property in joint names is itself useful on a future sale. Two owners bring two annual exempt amounts, GBP6,000 between them, and if one is a basic rate taxpayer, part of the gain can fall at 18% rather than 24%. Adjusting shares before a sale, while both owners are alive and, for spouses, while living together, is a recognised way to use both allowances and both rate bands.

Section 24 planning for joint owners

The planning that works for joint owners is unglamorous and evidence-driven. It is not about clever splits; it is about aligning who legally bears the income and the debt with who can relieve it most efficiently.

Shift income toward the lower rate owner

Where one owner is a basic rate taxpayer with spare band, moving a larger beneficial share to them keeps more rent and the matching credit at the lower rate. For spouses, that means a declaration of trust to set the real shares, then Form 17 to report on them. It works best when the lower rate owner has unused personal allowance or basic rate band, so the additional rent does not simply push them into higher rate. Run the numbers on both owners' total income, not just the property.

Think about ownership at the point of purchase

The cleanest time to set ownership shares is when you buy. Deciding shares up front, with the trust documentation in place, avoids the later transfer that can drag in SDLT on assumed debt. If you already know one owner will sit in the higher band, weighting beneficial ownership toward the basic rate owner at acquisition is far simpler than restructuring afterwards.

Watch the cliff edges, not just the headline rate

Because Section 24 adds the finance cost back before applying the credit, it can inflate adjusted net income and tip an owner over thresholds such as the GBP50,000 to GBP60,000 High Income Child Benefit Charge band or the GBP100,000 personal allowance taper. Splitting income across two owners can keep both below a cliff edge that one owner alone would breach. We unpack how the add-back pushes income up in can Section 24 push you into higher rate tax.

Maximise allowable deductions on each share

Section 24 only restricts finance costs. Every other allowable expense, letting agent fees, repairs, insurance, ground rent, accountancy, still reduces each owner's taxable profit in full and in proportion to their share. Splitting income across two owners also splits the deductions, so both should claim consistently. Our landlord tax deductions guide lists what each co-owner can claim against their share.

Reporting and Making Tax Digital for joint owners

Each owner reports their share independently on the UK property pages (SA105) of their own Self Assessment return. Income, allowable expenses and finance costs all go on each individual's return in their share, and the finance costs box drives the 20% credit. The two returns must tell a consistent story; you cannot split rent one way and expenses another without an election or agreement that supports it.

Making Tax Digital for Income Tax is now live and matters for joint owners because the threshold is tested per person, on each owner's own qualifying income. From 6 April 2026, owners with qualifying income above GBP50,000 must keep digital records and file quarterly updates. The threshold falls to GBP30,000 from 6 April 2027 and GBP20,000 from 6 April 2028. A 60/40 split can leave the larger owner inside MTD and the smaller owner outside it, so the same property can put the two of you on different filing regimes. Our guide to the Making Tax Digital deadline for landlords sets out the practicalities.

Partnerships and joint ownership: where the line sits

Owners sometimes assume that sharing rental profits makes them a partnership that can allocate profits freely. It rarely does. Most jointly let property is simple co-ownership, taxed on each owner's beneficial share, even where the owners actively manage the lettings together. A genuine partnership generally needs an organised business with a degree of services and commercial structure beyond ordinary letting. Where a real partnership does exist, profits follow the partnership agreement rather than the legal title, but Section 24 still applies and each partner's finance costs are still relieved only as a 20% credit. The partnership label does not escape the restriction; it only changes how the profit is allocated before the restriction bites.

Common mistakes joint owners make with Section 24

Getting Form 17 backwards

The most frequent and most expensive error is treating Form 17 as a way to choose a split. It is the election out of the 50/50 deeming and into the real beneficial shares, and it cannot create a split the trust does not support. A Form 17 filed without a matching declaration of trust, or to a split that does not reflect ownership, is invalid, and HMRC reverts you to 50/50.

Assuming the deed governs the split for spouses

Couples often report on their title shares and never realise s.836 has deemed them 50/50 the whole time. Where the deed and the desired tax split differ, you need the declaration of trust and Form 17, not just the deed.

Inconsistent reporting between the two returns

Each owner must report income and expenses on the same share. Splitting rent one way and interest another, with no election to support it, is the kind of inconsistency that invites an enquiry. Keep both returns aligned.

Forgetting the SDLT and CGT cost of restructuring

Reshaping ownership is not free of tax friction. Assumed mortgage debt can trigger SDLT (or LTT, or LBTT), and transfers to anyone other than a living-together spouse can trigger CGT at market value. Plan the restructure with both taxes in view, not just the income tax saving.

Looking ahead: the April 2027 separate property rates

The Finance Act 2026 enacted separate rates for property income from 6 April 2027. In England, Wales and Northern Ireland, property income will be taxed at 22% (basic), 42% (higher) and 47% (additional); only Scotland is carved out for 2027/28. The Section 24 credit rises in step to 22%, so a basic rate owner is no worse off and no new basic rate wedge opens. What changes is the gap between basic and higher property rates, which widens to 20 points. That makes moving income toward a lower rate owner more valuable than it is today, so couples should review their ownership shares and any Form 17 position before April 2027 rather than after. We cover the mechanics in how the 2027 property tax rates affect Section 24 relief.

For some heavily geared higher rate landlords, the better long-term answer is to sidestep Section 24 entirely, because companies still deduct finance costs in full. Whether that is worth the cost and complexity is a separate decision, weighed up in Section 24 versus incorporation.

Getting it right for your situation

Joint ownership and Section 24 reward precise paperwork. The income split has to match the beneficial ownership, the beneficial ownership has to be evidenced, and any change has to clear the CGT and SDLT consequences before it delivers the income tax saving. Where two owners sit at different rates, the difference between a default 50/50 position and a properly evidenced unequal split can be material, and the April 2027 changes raise the stakes. A specialist property accountant can model the split for your specific income profile and make sure the trust, the Form 17 and the returns all line up; our overview of what a property accountant does explains where that help fits.