The Shared Ownership Calculator works out the true monthly cost of buying a share of a property through a UK Shared Ownership scheme. Shared ownership lets you buy a share — typically between 10% and 75% — of a home from a housing association or other approved landlord via a Shared Ownership lease, taking out a mortgage on just that share and paying a deposit based on the share value rather than the full price. On the remaining share you don't own, you pay rent to the landlord, usually up to 2.75% of its value each year, plus a monthly service charge. Over time you can buy further shares in a process known as "staircasing", gradually increasing your ownership — and on most leases reducing your rent toward zero — until you may eventually own the property outright. This calculator shows your share value, deposit, mortgage payment, rent and total monthly cost, compares it against buying 100% outright, and gives an illustrative projection of what staircasing to a higher share could look like.
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This is a simplified, illustrative projection only. Real staircasing uses an independent valuation of the property at the time you buy the extra share, which may differ from today's market value — so treat the figures below as a guide to the mechanics, not a precise forecast.
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You're buying a share of a property through a Shared Ownership scheme, taking out a mortgage on just that share and paying rent to the landlord on the remainder, alongside a monthly service charge.
Based on the property's full market value and the share percentage you enter, the calculator works out your share value and deposit, the mortgage needed on the share, your monthly mortgage payment using the standard repayment formula, and the rent due on the unsold share — then adds everything together for your total monthly housing cost, alongside a comparison against buying the whole property outright.
Your calculation summary shows that for a £300,000 property, buying a 40% share (£120,000) with a 10% deposit on the share (£12,000), your mortgage on the share of £108,000 at 5.00% over 25 years costs £631.36 a month, plus £412.50 a month rent on the unsold 60% share and a £120.00 service charge — a total monthly cost of £1,163.86.
This calculator provides an illustrative estimate only. It doesn't account for mortgage fees, valuation fees, changes to the rent review mechanism, ground rent, buildings insurance, stamp duty/LTT/LBTT, or changes in the property's market value over time. Staircasing figures are a simplified projection assuming no change in market value and an extension of your existing mortgage with no further deposit — always get independent financial and legal advice, and a formal mortgage illustration, before making decisions.
Shared ownership is a UK government-backed scheme that lets you buy a share of a property — typically between 10% and 75% — from a housing association or other approved landlord, rather than buying the whole thing outright. You take out a mortgage to cover your share of the price, plus a deposit, and pay rent to the landlord on the share you don't yet own. It's designed to help people who can't afford to buy a home outright in the normal way, by shrinking the mortgage and deposit you need down to a fraction of the full property value.
Your monthly outgoings are made up of three parts: your mortgage payment on the share you own, rent on the share you don't, and a service charge covering the upkeep of communal areas and buildings insurance. Over time, you can buy further shares — known as staircasing — gradually increasing your ownership percentage and reducing the rent you pay, potentially up to owning the property outright.
To qualify for shared ownership in England, you generally need to: be a first-time buyer, or someone who used to own a home but can't afford one now, or an existing shared owner looking to move; and have a household income that doesn't exceed a set cap — historically £80,000 a year outside London and £90,000 a year in London, though these income caps have recently been increased for the first time in a decade to keep the scheme accessible, so always check the current figures for your area before assuming you're priced out. Priority is often given to current or former members of the armed forces, and some schemes give priority to people with an existing local connection to the area.
Under the 2021 model shared ownership lease — used for homes funded through the Affordable Homes Programme 2021–2026 — the minimum initial share was reduced from 25% to just 10% of the property's value, specifically to make the scheme accessible to buyers on lower incomes or with smaller deposits. The maximum initial share you can usually buy is 75%, though on many leases you can keep staircasing beyond that afterwards, often up to full ownership.
You pay rent to the landlord on the percentage share you don't own. The typical maximum rent charged is up to 2.75% of the unsold share's value per year, split into monthly payments. This rent is reviewed annually — usually on the anniversary of your lease start — and increased according to a formula set out in your lease. For shared ownership leases funded from October 2023 onwards, rent increases are capped at CPI (the Consumer Prices Index) plus 1 percentage point a year, with a floor of 0% so rent can't fall below its previous level even if CPI is negative. Older leases often used RPI (the Retail Prices Index) plus 0.5%, which can produce bigger year-on-year increases since RPI has historically tended to run higher than CPI.
Staircasing is the process of buying additional shares in your home after your initial purchase, increasing your ownership percentage. Under the 2021 model lease, further shares can be bought in increments as small as 5% (compared with 10% minimum tranches under older leases), and some newer leases also allow annual "mini-staircasing" purchases of just 1% for the first 15 years of ownership, with simplified paperwork and no formal valuation fee for those small tranches. Larger staircasing transactions require an independent valuation of the property at the time of the purchase — not the value when you originally bought — so the cost of each extra percentage point can be higher or lower than your original purchase price, depending on how the local market has moved. As you staircase up, the rent you pay on the remaining, smaller unsold share reduces proportionally, and on many leases you can staircase all the way to 100% ownership, after which no further rent is due.
Shared ownership purchases are still subject to property transaction tax — Stamp Duty Land Tax (SDLT) in England and Northern Ireland, Land Transaction Tax (LTT) in Wales, or Land and Buildings Transaction Tax (LBTT) in Scotland — but you get a choice in how it's paid. With a market value election, you pay the tax upfront based on the full market value of the property, even though you're only buying a share of it; once paid, you owe nothing more even if you staircase to 100% later. Alternatively, you can pay in stages: tax is due on your initial share premium (if it's above the relevant threshold), and then nothing further is owed until your total staircased share passes 80% of the property, at which point a return must be filed and tax paid on that transaction and every one after it. Use our dedicated SDLT, LTT or LBTT calculators to work out the figure that applies to your region and chosen payment method.
On top of your mortgage and rent, shared owners pay a monthly service charge covering buildings insurance, maintenance of communal areas (such as stairwells, lifts, gardens and shared parking), and often a management fee to the landlord or managing agent. You pay the full service charge regardless of what percentage share you own — it isn't reduced just because you own less than 100% of the property, which is an easy point to overlook when budgeting. Ground rent is less common on modern shared ownership leases, but where it applies it's usually a small, fixed or peppercorn (nominal) amount — always check your specific lease, since service charges in particular vary significantly by development and tend to rise over time as maintenance and insurance costs increase.
You can sell your share of a shared ownership property, but the process usually differs from an open-market sale. Most leases give the landlord a "right of first refusal" — often called the nomination period, typically lasting around 4 to 8 weeks — during which the landlord can try to find a buyer from their own waiting list of shared ownership applicants, usually at a price based on an independent valuation. If the landlord can't find a buyer within the nomination period (or if your share has passed a certain threshold, often 80%, on some leases), you're generally free to market the property yourself on the open market, though the buyer will usually need to go through a similar shared ownership purchase process for your share.
Take a £300,000 property, where a buyer purchases a 40% share. That share is worth £120,000 (40% of £300,000). With a 10% deposit on the share value, the deposit is £12,000, leaving a mortgage of £108,000. At a 5% mortgage rate over a 25-year term, the monthly mortgage payment works out at around £631.36. The remaining 60% share, worth £180,000, is rented from the landlord at 2.75% a year, which is £4,950 a year or £412.50 a month. Adding a typical £120 monthly service charge gives a total monthly housing cost of around £1,163.86 — compared with an estimated £1,803.62 a month if the same buyer had taken a full mortgage (at the same rate and term) to buy the whole £300,000 property outright with the same £12,000 deposit.
This calculator focuses on the ongoing cost of shared ownership — your share value, deposit, mortgage, rent and total monthly cost. If you want to explore a standard mortgage on a full property instead, try our Mortgage Repayment Calculator, or our Mortgage Affordability Calculator to see how much you might be able to borrow. For the tax due on your purchase, use our SDLT, LTT or LBTT calculators depending on where the property is located.