First-time buyer joint mortgage: buying with someone else

How does a first-time buyer joint mortgage work?

A first-time buyer joint mortgage is one mortgage in two or more names: the lender adds your incomes together to decide how much to lend, and every person named on it is responsible for the whole debt, not just their share. Most lenders allow up to four borrowers, though Halifax notes that most joint mortgages are couples and NatWest only offers them to two people (Halifax, NatWest). Buying with a partner, a sibling or a friend all work the same way in law; the difference is how much you trust each other and how carefully you write things down.

The liability point is the one to understand first. MoneyHelper puts it plainly: by signing a joint credit agreement “you’re each agreeing to pay off the whole amount if the other(s) can’t or won’t pay”, whoever spent the money (MoneyHelper). If your co-owner stops paying, the lender comes to you for all of it, and a missed payment marks both credit files.

How do lenders count two incomes?

They add them together and apply the same multiple. Halifax says lenders generally let you borrow “around four times your yearly income” and that with a joint mortgage “you might be able to borrow up to four times your combined income” (Halifax); MoneyHelper puts the usual cap at four and a half times, “but this isn’t guaranteed” (MoneyHelper). So two salaries of £28,000 and £24,000, £52,000 together, support borrowing of roughly £208,000 to £234,000. The higher earner alone would get about £112,000 to £126,000.

The multiple is only the ceiling. Every lender then runs an affordability check on both applicants’ outgoings, debts and credit files, and Halifax warns that once you apply together “your credit profiles become connected”, so one person’s missed payments can sink the application or hurt the other’s score (Halifax). Both of you should check your credit reports before you apply, not after. The mortgage required calculator shows the household income a given price needs.

Joint tenants or tenants in common: which should you choose?

You must pick one when you buy, and it decides what happens if you fall out or one of you dies. As joint tenants “you have equal rights to the whole property”, the home “automatically goes to the other owners if you die”, and you “cannot pass on your ownership of the property in your will”. As tenants in common “you can own different shares of the property”, your share “does not automatically go to the other owners if you die”, and you can leave it in your will (GOV.UK).

Couples who want everything shared often choose joint tenants. Friends, siblings, and couples putting in unequal deposits usually choose tenants in common, because it lets a 70/30 contribution be recorded as a 70/30 ownership. You can change later: a joint tenant can switch to tenants in common by sending HM Land Registry Form SEV, there is no fee, and you do not need the other owner’s agreement, though you must serve them written notice (GOV.UK). The Land Registry then adds a restriction to the register showing the change.

What is a declaration of trust?

A declaration of trust, also called a deed of trust, is a legal document that records who owns what share of the home, who paid what towards it, and how the money is split if you sell. It sits behind a tenants in common arrangement and is drawn up by your conveyancer at the time you buy. The HomeOwners Alliance describes it as setting out “when and how the property can be sold” and “how the net sale proceeds should be divided up” (HomeOwners Alliance).

It matters most when contributions are unequal. If one of you puts in a £20,000 deposit and the other £5,000, and you own as joint tenants, the law presumes you own the home equally and the £15,000 difference is not automatically recognised on a sale. A declaration of trust can say the £20,000 comes back first, or that the shares are 60/40, or whatever you agree. Ask your conveyancer for a fixed price before you instruct them; it is a routine document, not an exotic one.

Do you both have to be first-time buyers?

For stamp duty relief, yes. GOV.UK says you are eligible “if you and anyone else you’re buying with are first-time buyers” (GOV.UK). HMRC’s manual defines a first-time buyer as someone who “must not, either alone or with others, have previously acquired a major interest in a dwelling or an equivalent interest in land situated anywhere in the world”, including by inheritance or gift (HMRC manual SDLTM29845). One previous owner among the buyers means no relief for anyone.

For the government equity loan, we expect the same. Your First Home is for first-time buyers (GOV.UK), and its predecessor Help to Buy said “you and anyone you’re buying a home with must not own, or have ever owned, a home or residential land now or in the past in the UK or abroad” (GOV.UK). Until the Budget on 28 October 2026 publishes the new rules, that is an assumption, and the eligibility page will carry the confirmed wording. For the Lifetime ISA, each of you must qualify separately, and if you both do “you can both use your savings and government bonus” on the same home (GOV.UK).

What happens if one of you owned a home before?

You lose first-time buyer relief on the whole purchase, and probably the scheme. Take a couple buying a £350,000 home where one partner once owned a flat: as two first-time buyers they would pay £2,500 in stamp duty; because one has owned before, they pay the standard £7,500 (GOV.UK). Above £500,000 the difference disappears, because nobody gets relief there anyway. The stamp duty page has the bands.

Some people consider buying in one name only. That has real consequences: the person not on the deeds has no automatic right to the home, and the lender will only count the income of the person it is lending to. Anyone weighing it should take legal advice; this site describes the rules and does not advise on ways round them.

What happens if one of you wants to leave?

The mortgage does not care about your relationship. Both of you remain liable until the loan is repaid or the lender agrees to remove a name. There are two clean exits. You sell, repay the mortgage and split what is left as your ownership type and any declaration of trust dictate. Or one of you buys the other out through a transfer of equity, which means the lender re-checks that the remaining owner can afford the mortgage alone; if they cannot, the lender can refuse. NatWest’s advice is to “contact your lender to discuss the options available to you” as the first step (NatWest). Agreeing in writing, at the start, how a buyout would be valued saves an argument later.

Worked example: two salaries, one £230,000 new build

Two first-time buyers earning £28,000 and £24,000 want a £230,000 new-build house. Their joint income is £52,000, so a lender working at four and a half times would lend up to £234,000. With a 5% deposit of £11,500 they need a £218,500 mortgage, 4.2 times income, which fits but costs about £1,351 a month at 5.57%, the best 95% two-year fix on 26 September 2026 (HomeOwners Alliance).

Under Your First Home’s expected rules the deposit falls to £5,750, the government lends £46,000, and the mortgage is £178,250, 3.4 times their income, at about £1,042 a month on the 5% two-year fix available at that loan-to-value from a lender operating across England (HomeOwners Alliance). The higher earner alone, capped at about £126,000, could not borrow either amount. Both are first-time buyers, so stamp duty is £0. The calculator runs your own numbers.

What to do next

• Check both credit reports, then get a joint agreement in principle to see what lenders will actually offer.
• Decide joint tenants or tenants in common before you instruct a conveyancer, and ask for a declaration of trust quote if your contributions differ.
• Confirm that everyone buying is a first-time buyer for stamp duty and, after the Budget on 28 October 2026, for Your First Home.
• Budget for the fees as well as the deposit, and agree in writing who pays what.