Shared ownership calculator
Shared ownership cost combines three separate charges: a mortgage on the share purchased, rent on the share the housing association retains, and a service charge. For a 25% share of a £300,000 home, the example below comes to £978 a month in total. The gov.uk Shared Ownership scheme page sets out the rules behind each part.
How does the monthly cost split?
| Part | Per month |
|---|---|
| Mortgage on your share | £362 |
| Rent on the landlord's share | £516 |
| Service charge | £100 |
| Total | £978 |
How does shared ownership cost work?
A buyer purchases a share of the home, commonly between 25% and 75% of its value. A mortgage and deposit cover that share. Rent is charged on the remaining share, which the housing association keeps, normally at an annual rate of around 2.75% of the unowned value, as set out on the gov.uk Shared Ownership scheme page. A service charge is added on top because the property is usually leasehold. Buying a larger share raises the mortgage and lowers the rent, so the cheapest monthly total is not always the smallest share.
What would I pay in a worked example?
Take a £300,000 home and a 25% share worth £75,000. With a 10% deposit the mortgage is £67,500, costing £362 a month at 5.0% over 30 years. Rent on the £225,000 share not owned adds £516. The service charge adds £100. The total is £978 a month, or £11,736 a year.
Common questions
How does the monthly cost split?
The monthly figure has three parts: the mortgage on the share bought, the rent on the share not owned, and a service charge that applies to the whole property. In the example on this page, a 25% share of a £300,000 home comes to £362 in mortgage, £516 in rent and £100 in service charge, for a total of £978 a month.
How does shared ownership cost work?
A mortgage is paid on the share bought and rent on the share the landlord keeps, plus a service charge. Buying a 25% share of a £300,000 home in this example costs about £978 a month: £362 mortgage, £516 rent and £100 service charge.
How is the rent on a shared ownership home worked out?
The rent is charged on the share you do not own, usually at an annual rate of around 2.75% of that unowned value, set when you buy. So the smaller the share you buy, the more rent you pay, because the landlord owns more of the property. The rate can rise each year under the terms of the lease.
Is a bigger share always cheaper each month?
Not necessarily. A bigger share means a larger mortgage but less rent, and mortgage rates and rent rates differ, so the monthly total can move either way. Buying more of the home, known as staircasing, also needs a bigger deposit and valuation, so it is worth modelling the monthly cost at a few different share sizes before deciding.
Do I pay stamp duty on shared ownership?
You can, but there are choices. You either pay stamp duty on the full market value up front, or pay in stages as you buy bigger shares. Many first-time buyers pay nothing initially because the share value is below the threshold. Check the current rules, as the stamp duty treatment of shared ownership is specific and can change.
What is staircasing?
Staircasing is buying additional shares in your home over time, up to 100% in most cases. Each purchase increases your mortgage and reduces the rent you pay, and once you own the whole property the rent stops. There can be valuation and legal fees each time you staircase, so it is not free to do.
Does the service charge still apply?
Yes. Shared ownership homes are usually leasehold, so a service charge applies to the whole property regardless of the share you own. That is why it is a separate line here rather than being scaled to your share. It can rise year to year like any leasehold service charge.
What would I pay in a worked example?
On a £300,000 home, a 25% share is worth £75,000. With a 10% deposit the mortgage is £67,500, costing £362 a month at 5.0% over 30 years. Rent on the £225,000 share not owned adds £516, and the service charge adds £100. The total comes to £978 a month, or £11,736 a year.
Sources & Rate Verification
Rates verified against official statutory guidance on 6 September 2026.