Working out what it costs to buy someone out of a house is rarely just a sum. It usually arrives alongside a separation, a divorce, or an inheritance being divided between siblings, and the arithmetic has to be done at exactly the moment you have least appetite for it.
The good news is that the calculation itself is straightforward, and it is the same whether the property is a one-bedroom flat off Northcote Road or a family house on Bellevue Road. Four figures decide almost everything: what the property is worth, what is left on the mortgage, how the ownership is split, and what the tax and fees add on top.
This guide walks through each of those in order, with a calculator you can use as you go, worked examples using current south west London prices, and the two rules that catch people out most often. One of them depends entirely on whether you were married.
- The core sum is simple. Property value minus outstanding mortgage gives net equity. Multiply that by the departing owner's share and you have the buyout figure.
- Get two numbers in writing first. A market appraisal for the value, and a redemption statement from the lender for the exact mortgage balance including any early repayment charge.
- Married and unmarried couples are taxed completely differently. Spouses and civil partners separating are usually exempt from stamp duty. Cohabiting couples are not.
- Stamp duty is charged on more than the cash you hand over. The taxable amount includes the share of the mortgage you take on, which is why people underestimate it.
- The lender, not the solicitor, is usually the bottleneck. You will need to pass affordability on a single income before anything else can complete.
- Allow four to eight weeks for a straightforward transfer of equity, longer where a remortgage or a dispute is involved.
Buyout calculator
Enter the four figures below and the calculator works out the net equity, what the departing owner is owed, the likely stamp duty, and the size of mortgage you would need if you funded the whole buyout by borrowing. Adjust the ownership split if you do not own the property equally.
A worked buyout exampleWork out your buyout figure
Worked example: a £750,000 home with a £320,000 mortgage, owned equally. The figures below show how it divides.
Indicative only. Confirm every figure with your lender, conveyancer and a tax adviser.
- Net equity in the property£430,000
- Your share of the equity£215,000
A calculator can only work with the figures you give it. The two that people guess at are the property value and the mortgage balance, and both need to come from somewhere official. Book a free market appraisal for the first, and ask your lender for a redemption statement for the second.
What buying someone out actually involves
Buying someone out means one co-owner purchases the other's share of the property, so that ownership passes to a single person without the home going on the open market. The legal mechanism is called a transfer of equity, and it updates the ownership recorded at HM Land Registry.
It comes up in three situations more than any other: couples separating, siblings dividing an inherited property, and friends who bought together and now want different things. In each case the person staying pays the person leaving their share of the equity, and normally takes on the mortgage alone.
To calculate buying someone out of a house in the UK, subtract the outstanding mortgage from the current market value to get the net equity, then multiply the net equity by the departing owner's percentage share.
(Property value − Outstanding mortgage) × Their share = Buyout figureOn a property worth £750,000 with £320,000 outstanding and equal ownership, the net equity is £430,000 and the buyout figure is £215,000. Stamp duty, legal fees and lender charges are then added on top.
One point matters more than any other before you go further. Until the transfer completes, everyone named on the mortgage remains jointly and severally liable for it. If payments are missed, the lender can pursue any one of you for the full amount, regardless of who is living there or who agreed to pay what. That liability ends only when the paperwork is finished, not when you shake hands on a figure.
The five steps, in order
Do these in sequence. Skipping straight to the split is the most common reason a buyout figure gets challenged later.
- 1 Allow 1 to 2 weeks Establish the current market value
You need a defensible figure, not a portal estimate. A local market appraisal is free and reflects what is actually selling on your street. A formal RICS valuation costs more but carries weight with lenders and in court, which matters if the two of you disagree. Many people get both. Our guide to what a mortgage valuation involves explains how a lender's own assessment differs from either.
- 2 Allow 5 to 10 working days Request a mortgage redemption statement
This is the step people skip, and it changes the answer. Your annual statement shows a balance. A redemption statement shows the exact figure to clear the loan on a given date, including accrued interest and, critically, any early repayment charge. Those charges typically run at 1% to 5% of the balance, so on a £320,000 mortgage an ERC could add £3,200 to £16,000 to the cost of restructuring. Ask the lender for it in writing before you agree anything.
- 3 Same day Calculate the net equity
Subtract the redemption figure from the market value. What remains is the net equity, and it is the only pot available to divide. If there is a second charge, a secured loan or a Help to Buy equity loan on the property, deduct that too.
- 4 Check the title first Apply the ownership split
How you own the property decides how the equity divides. Joint tenants split equally by default. Tenants in common split according to the declaration of trust. A court can override both. Check the title register rather than relying on memory, because a surprising number of people are not certain which applies to them.
- 5 Same day Arrive at the buyout figure, then add the costs
Net equity multiplied by the departing owner's share gives the payment due. That is not the full cost. Stamp duty, legal fees, lender fees and any capital gains tax sit on top, and they are covered further down this page.
Joint tenants or tenants in common: check before you calculate
This single distinction changes the answer, and it is recorded on the title register rather than being a matter of what feels fair. If you are unsure which applies, your conveyancer can confirm it in minutes.
Joint tenants
You own the whole property together, with no separate shares. The equity is normally split 50/50 between two owners, regardless of who paid the larger deposit or made more of the repayments.
- Equal split by default
- Right of survivorship: if one owner dies, their interest passes automatically to the other
- Cannot be left to someone else in a will
- Can be converted to a tenancy in common by severing the joint tenancy
Tenants in common
Each owner holds a defined share, which can be equal or unequal. Those shares are usually set out in a declaration of trust drawn up at purchase, and that document governs the buyout.
- Split follows the declared percentages, for example 70/30
- No right of survivorship
- Each share can be left to someone else in a will
- Where no declaration exists, shares may need to be established by evidence or by the court
A court order can override either arrangement. In divorce and dissolution proceedings, a property adjustment order can reallocate shares entirely, which is why a couple who own as joint tenants may still end up dividing the equity 60/40 or 70/30. You can check the two forms of ownership on GOV.UK's joint property ownership guidance.
Unmarried couples who bought as tenants in common without recording their shares are in the hardest position. Establishing who owns what then depends on contributions, conduct and any evidence of a common intention, and resolving it can mean a claim under the Trusts of Land and Appointment of Trustees Act. Taking legal advice early costs considerably less than litigating later.
Buying someone out when there is no mortgage
Where the property is owned outright, the calculation gets simpler and the tax gets more expensive. This is the common position with inherited property, and it catches siblings out regularly.
With no mortgage to deduct, the net equity is simply the market value. On a property worth £800,000 owned equally by two siblings, each share is £400,000, and the one staying pays the other £400,000.
The complication is stamp duty. Because there is no mortgage to take on, the entire chargeable consideration is the cash you pay, and cash is fully taxable. Worse, if the sibling buying out already owns their own home, the 5% additional property surcharge applies on top, because they are not replacing a main residence.
| Buyer's position | Chargeable consideration | Stamp duty due |
|---|---|---|
| Does not own another property | £400,000 | £10,000 |
| Already owns their own home | £400,000 | £30,000 |
That £20,000 difference is the surcharge alone, and it is the single largest avoidable shock in an inherited property buyout. The position can be affected by how and when the inheritance was received, so this is a point to put to a tax adviser before you commit to a figure rather than after.
Timescales are the compensation. With no lender consent to obtain, a transfer of equity on an unencumbered property can complete in three to four weeks rather than six to eight.
Married or not: the difference that costs the most
Almost every guide to buying someone out treats all couples the same. The tax system does not. Whether you were married or in a civil partnership changes the stamp duty position, the capital gains position, and what a court can do about the split. On a south west London property the gap between the two runs comfortably into five figures.
| Married or civil partners | Cohabiting, not married | |
|---|---|---|
| Stamp duty on the buyout | Normally exempt where the transfer is made because of divorce, dissolution or a formal separation agreement. HMRC does not need to be told. | Payable in the normal way, on the cash paid plus the share of mortgage taken on. |
| Capital gains tax on the transfer | No gain, no loss treatment for up to three tax years after the year you stop living together, and no time limit at all where the transfer is part of a formal divorce agreement. | Treated as a disposal at market value. Private residence relief may cover a main home, but any second property is exposed. |
| Can a court reallocate the shares | Yes. A property adjustment order can depart from the legal ownership entirely. | No. The declaration of trust governs, unless a claim is brought under trusts of land legislation. |
| Right to stay in the home while it is resolved | Home rights can be registered against the title even where only one spouse is the legal owner. | No automatic right where you are not on the title. |
There is a relief that is barely mentioned in consumer guidance. If your name is still on the former family home, that interest can be disregarded when you buy a new main residence, provided the old home is your ex-partner's only or main residence and a property adjustment order or consent order is in place over it. Without that relief, the 5% surcharge on a £900,000 purchase would be £45,000. The relief depends on there being a formal order, so an informal separation will not qualify. Take advice on this specifically.
Stamp duty on a buyout, and why the figure surprises people
The mistake is assuming stamp duty is charged on the cash you hand over. It is charged on the chargeable consideration, which is the cash plus the share of the outstanding mortgage you take on. Taking over your co-owner's half of a £400,000 mortgage adds £200,000 to the taxable amount before a penny changes hands.
The worked example on GOV.UK's own transfer of ownership guidance has not been updated since September 2022 and still applies the old £250,000 nil rate band, giving stamp duty of £1,250 on that £275,000. Under the thresholds in force since 01/04/2025 the correct figure is £3,750. Several widely read articles have copied the outdated number. If a calculator or guide gives you £1,250 on these facts, it is working from stale rates.
| Portion of the chargeable consideration | Standard rate | With the 5% surcharge |
|---|---|---|
| Up to £125,000 | 0% | 5% |
| £125,001 to £250,000 | 2% | 7% |
| £250,001 to £925,000 | 5% | 10% |
| £925,001 to £1,500,000 | 10% | 15% |
| Above £1,500,000 | 12% | 17% |
Two thresholds matter alongside the rates. Below £40,000 of chargeable consideration, no return is required at all. Between £40,000 and £125,000, a return is required but no tax is payable. Above £125,000, tax is due, and the return must be filed within 14 days of completion either way. Our full guide to stamp duty covers the wider rules, and if the surcharge is in play, stamp duty on second homes goes into more detail. HMRC's own position is set out in its guidance on transferring ownership of land or property.
Capital gains tax on the departing owner
Capital gains tax falls on the person leaving, not the person staying, and in most straightforward cases it does not arise at all. Where the property has been the departing owner's main home throughout, private residence relief normally covers the gain in full, and the final nine months of ownership always qualify for relief regardless of whether they were still living there.
It becomes a real cost in three situations: where the property was let or was a second home, where an unmarried couple are dividing an investment property, and where a separated spouse transfers outside the permitted window.
| Item | Position |
|---|---|
| Basic rate taxpayer | 18% on the residential property gain |
| Higher rate taxpayer | 24% on the residential property gain |
| Annual exempt amount | £3,000 for individuals |
| Reporting and payment | Within 60 days of completion where tax is due |
| Spouses and civil partners separating | No gain, no loss for up to three tax years after the year of separation. No time limit under a formal divorce agreement. |
If the departing owner is keeping an interest in the property under a deferred arrangement, or is receiving a share of the proceeds on a future sale, the treatment is more involved and worth taking advice on. GOV.UK sets out the basics on tax when you sell your home.
The full cost of a buyout, itemised
The buyout payment is the headline. These are the figures that sit underneath it, and planning for them early is what keeps a transfer on track.
| Cost | Typical range | Who normally pays |
|---|---|---|
| Transfer of equity conveyancing | £600 to £1,200 | The owner staying, though this is negotiable |
| Independent legal advice for the departing owner | £250 to £600 | The owner leaving |
| RICS valuation report | £350 to £900+ | Usually shared |
| Mortgage arrangement or product fee | £0 to £2,000 | The owner staying |
| Early repayment charge, if you break a fix | 1% to 5% of the balance | The owner staying |
| HM Land Registry fee, electronic | £20 to £140 | The owner staying |
| Telegraphic transfer fee | £25 to £50 | The owner staying |
| Stamp duty | Varies, often £0 | The owner staying |
| Capital gains tax | Varies, often £0 | The owner leaving |
The early repayment charge deserves particular attention because it is the largest of these by some distance and the easiest to overlook. On a £400,000 mortgage in the second year of a five year fix, a 4% charge is £16,000. It is sometimes less expensive to arrange a further advance with your existing lender and leave the original loan intact than to remortgage away and trigger it. Our guide to conveyancing fees sets out the legal side in more detail.
How people actually fund the buyout
Knowing the figure is one thing. Producing it is another, and this is where most buyouts either work or fall over.
Remortgage into your sole name
The most common route. You take a new mortgage large enough to clear the existing loan and release the buyout payment. The lender reassesses affordability on your income alone.
- Removes the departing owner from the mortgage
- Lets you shop the whole market for rate
- May trigger an early repayment charge on the existing loan
Further advance from your current lender
Additional borrowing on top of the existing mortgage, from the lender you already have. Often quicker, and it avoids breaking a favourable fixed rate.
- Usually faster than a full remortgage
- Protects an existing low rate on the original loan
- The new borrowing may be priced differently
Savings, family help or a mix
Where the buyout figure is modest relative to the equity, cash or family support can cover it without increasing the borrowing at all.
- Avoids affordability assessment entirely
- Family gifts need to be evidenced for the lender and for anti money laundering checks
- Keeps the monthly cost unchanged
The affordability test is the real hurdle
Going from two incomes to one, while increasing the loan, is a demanding combination. A couple who comfortably supported a £500,000 mortgage together may find that a £600,000 mortgage on one salary sits outside what any lender will offer.
Borrowing capacity has improved. Most lenders work to four and a half to five times income, and through 2025 and 2026 several extended higher multiples to movers and remortgage customers, with six times income available on some products where income clears £75,000 for a sole applicant. Those thresholds are exactly the range a good number of buyers across SW11, SW12 and SW18 will meet, and it has made single income buyouts viable in cases where they would not have been three years ago.
What has not changed is the arithmetic of it. Work out your maximum borrowing before you agree a buyout figure, not after. Agreeing a number you cannot fund wastes months and sours a negotiation that may already be difficult.
Get a decision in principle in your sole name before you open the conversation about figures. It converts an argument about fairness into a conversation about what is actually possible, and it gives you a defensible reason for the position you are taking.
What to do if you cannot afford to buy them out
This is a common outcome and not a failure. There are more options than most people realise, and several of them keep you in the property.
- Extend the mortgage term. Moving from 15 remaining years to 25 materially reduces the monthly payment and can bring affordability within reach, at the cost of more interest overall.
- Offer a smaller cash sum plus a deferred share. The departing owner takes less now in return for a percentage of the proceeds when the property is eventually sold. This needs a properly drafted deed, not a handshake.
- Add a joint borrower. Some lenders allow a family member's income to support the mortgage without them owning a share, which avoids handing them a stamp duty problem.
- Delay the sale until a trigger point. In divorce cases the court can order that the home is not sold until the youngest child finishes school, with the equity divided at that point.
- Let the property and rent elsewhere. Where neither party can afford to buy the other out immediately, letting it can service the mortgage while values and circumstances change. Our guide to letting a property for the first time covers what that involves, and consent to let is needed from the lender.
- Sell and divide the proceeds. Sometimes the cleanest answer. If you go this way, understanding how long a sale typically takes helps you plan, and what stalls a sale is worth reading before you launch.
The legal process, step by step
Once the figure is agreed and the funding is arranged, the transfer itself is handled by a solicitor or licensed conveyancer. You cannot sensibly do this yourself where a mortgage is involved, and most lenders will not deal with an unrepresented party.
- 1 Instruct a conveyancer and get the lender's consent
The lender must agree to release the departing owner from the mortgage. This is the step that sets the timetable, and no amount of pressure on the solicitor speeds it up. Choosing the right firm matters, and our guide on whether you need a conveyancer or a solicitor explains the difference.
- 2 Both parties take independent advice
The departing owner should have their own representation. Lenders often insist on it, and it protects the transfer from being challenged later on the grounds that someone did not understand what they were signing.
- 3 Forms TR1, AP1 and ID1 are prepared
TR1 transfers the whole of the registered title. AP1 applies to change the register. ID1 verifies identity where digital verification is not possible, which is most common for an unrepresented party. Most conveyancers now verify identity digitally under HM Land Registry's digital identity standard.
- 4 Completion, payment and the stamp duty return
Funds transfer, the departing owner is paid, and the mortgage is redeemed or varied. The stamp duty return must be filed within 14 days of completion even where no tax is due, unless the transaction is exempt.
- 5 Registration at HM Land Registry
The application updates the title. Roughly half of applications to update the register are dealt with within a week, but a meaningful proportion take considerably longer. This does not delay completion or affect your ownership. The transfer is effective on completion, and the register catches up.
A transfer of equity with no mortgage can complete in three to four weeks. With a mortgage and a straightforward lender, four to six weeks is realistic. Where a full remortgage is needed, or where the two parties are not in agreement, six to eight weeks or more is common. The variable is almost always the lender, not the paperwork.
Three worked examples on the patch
The figures below use official Wandsworth averages for May 2026 and illustrative mortgage balances. They show how differently the same calculation lands depending on marital status and whether there is a mortgage at all.
A flat, a joint mortgage, and no marriage certificate
A couple own a flat worth £509,000 as joint tenants, with £280,000 outstanding. They are not married. One wants to stay.
- Net equity£229,000
- Buyout payment£114,500
- Chargeable consideration (cash plus £140,000 mortgage share)£254,500
- Stamp duty, payable because they are not married£2,725
- New mortgage required£394,500
- Cash needed on top of borrowing£2,725 plus fees
Had they been married and separating, the stamp duty would be nil. That is the whole difference on an otherwise identical transaction.
A family house, a court order, and an unequal split
A married couple own a terraced house worth £926,000 with £340,000 outstanding. A court order allocates 60% of the equity to the parent with primary care of the children.
- Net equity£586,000
- Buyout payment£234,400
- Stamp duty, exempt under the court order£0
- New mortgage required£574,400
- Resulting loan to value62%
The staying owner must still satisfy a lender that a £574,400 mortgage is affordable on one income. At five times income that needs roughly £115,000 of earnings, before any maintenance obligations are taken into account.
An inherited house, owned outright, one sibling already a homeowner
Two siblings inherit a house worth £800,000 with no mortgage, held equally. One wants to keep it. She already owns a flat.
- Net equity, no mortgage to deduct£800,000
- Buyout payment£400,000
- Stamp duty at standard rates£10,000
- Additional property surcharge, because she owns a flat£20,000
- Total stamp duty£30,000
Three times the tax, on identical facts, purely because she owns another property. Whether selling her flat first improves the position depends on timing and on her own circumstances, which is precisely the sort of question to put to a tax adviser before committing.
Where buyouts go wrong
Financial
- Planning around the buyout figure alone and forgetting stamp duty, legal fees and lender charges
- Missing an early repayment charge that makes remortgaging the wrong route
- Agreeing a figure before checking what you can actually borrow
- Using a portal estimate rather than a proper appraisal, then finding the lender's valuation comes in lower
Legal
- Assuming a 50/50 split when the title says tenants in common with unequal shares
- Attempting the transfer without a conveyancer and getting the Land Registry paperwork wrong
- Relying on a verbal agreement about a deferred payment rather than a drafted deed
- Forgetting to update the will, which after a severed joint tenancy is no longer academic
Practical
- Missing mortgage payments during the process, which damages both parties' credit files and can derail the remortgage
- Leaving utilities, insurance and standing orders in joint names after completion
- Not agreeing who pays the mortgage in the interim, in writing
Interpersonal
- Letting the valuation become a proxy for the wider argument
- Negotiating directly when a solicitor or mediator would resolve it faster and for less
- Allowing the process to drift, while the fixed rate expiry and the market both move
Start with a number you can rely on
Every calculation on this page rests on the property's current value. We have been valuing homes around the commons since 2008, across Battersea, Clapham, Balham, Wandsworth and Earlsfield, and we know what is genuinely achievable street by street rather than what a portal algorithm suggests.
If you are working through a separation or dividing an inherited property, a conversation with someone who has seen it many times before is often worth more than another calculator.
Frequently asked questions
How do you work out how much to buy someone out of a house?
Subtract the outstanding mortgage from the current market value to get the net equity, then multiply that by the departing owner's percentage share. On a £600,000 property with a £250,000 mortgage and equal ownership, the equity is £350,000 and the buyout figure is £175,000. Stamp duty, legal fees and lender charges are added on top.
Do you pay stamp duty when buying someone out of a house?
Often yes, and it is charged on more than the cash you pay. The taxable amount is the cash plus the share of the mortgage you take on. The important exception is that transfers between spouses or civil partners made because of divorce, dissolution or a formal separation agreement are normally exempt. Cohabiting couples do not get that exemption.
How do you calculate a buyout when there is no mortgage?
With no mortgage the net equity is simply the market value, so on a £800,000 property held equally each share is £400,000. Stamp duty tends to be higher in this situation, because the whole payment is cash and cash is fully chargeable. If the person buying already owns another property, the 5% surcharge can apply on top.
Can you partially buy someone out of a house?
Yes. Where both parties agree, one owner can transfer part of their share, changing the percentages held rather than removing a name entirely. It still requires a transfer of equity, an updated declaration of trust, and the lender's consent where there is a mortgage.
How is a divorce house buyout calculated?
It starts from the same equity calculation, but the split does not have to follow the legal ownership. A court can make a property adjustment order that departs from a 50/50 position to reflect childcare responsibilities, income differences, pension arrangements and the length of the marriage. The buyout figure then follows whatever the order specifies.
How do you buy a sibling out of an inherited house?
Value the property, deduct any mortgage, and pay the sibling their share of the equity, usually funded by a mortgage on the inherited property or by savings. The point to check early is stamp duty. If you already own a home, the additional property surcharge can add 5% of the whole chargeable amount, which on a £400,000 buyout is £20,000.
What are the downsides of buying out a partner on a mortgage?
You take on the full mortgage on a single income, which usually means a higher monthly payment and less financial flexibility. You may trigger an early repayment charge, and you lose the second income that supported the loan. Against that, you keep the home, keep any future growth in its value, and avoid the cost and disruption of selling and moving.
This guide covers England and Northern Ireland. Scotland and Wales operate separate property tax systems. Rates and thresholds stated are those in force at the date of publication and may change. Tax treatment depends on individual circumstances. Rampton Baseley are estate and letting agents, not solicitors or tax advisers, and nothing on this page is legal, tax or financial advice. Take professional advice before acting. Price data: Office for National Statistics and HM Land Registry UK House Price Index, May 2026, provisional.