Shared Ownership combines a mortgage on the share you own with rent on the share you have not bought. You may also pay service charges and other lease costs. Comparing only the mortgage with a full-home mortgage can therefore miss a large part of the monthly budget.
The Shared Ownership Cost Planner lets you enter your current mortgage payment, rent and charges, then compare them with an illustrative plan to buy a larger share. Use the amounts from your offer, lease, landlord and lender; this is not an affordability decision.
The monthly costs to include
Your ongoing housing budget may include:
- mortgage payment on the share you own;
- rent paid to the landlord on the remaining share;
- service charge for communal areas or building management;
- estate charge, management fee or repairs reserve contribution;
- buildings insurance and maintenance costs; and
- any other lease or lender charges.
The exact list depends on the property and lease. GOV.UK advises applicants to review the mortgage, rent and monthly charges together. Ask the landlord for a service-charge summary and what the charge covers. A low initial rent does not establish that future rent reviews or service charges will stay low.
How staircasing changes rent and borrowing
Staircasing means buying an additional share. In general, the rent is based on the share that remains with the landlord, so buying a larger share can reduce the rent. It also requires money to buy that share, usually from savings or additional mortgage borrowing.
For a simple illustration, if a home is valued at £300,000 and you buy another 15% share, the share price at that valuation is £45,000 before fees. GOV.UK’s tenant guide gives an example where a 40% owner pays £413 monthly rent; after buying another 15% and owning 55%, the example rent becomes £309. Your lease may use a different rent calculation or review, so use your landlord’s revised figure when available.
The cost of an additional share is not necessarily based on the original purchase price. Under the Right to Shared Ownership guidance, a standard additional share is priced using the home’s value at the time of staircasing and requires a RICS-registered valuation. A landlord may charge an administration fee, and a solicitor may need to update the lease. The specific options, minimum share sizes and charges depend on the scheme and lease.
The Right to Shared Ownership guidance also describes gradual staircasing by 1% per year during an initial period, and standard staircasing by 5% or more. These are scheme-specific terms: do not assume they apply to every Shared Ownership lease or transaction. Check your own lease and ask the provider what share sizes it permits.
Use a current lease figure, not a generic rent rate
The planner holds the current monthly service and other charges constant. It estimates future rent by scaling your entered rent in proportion to the unsold share. That is a planning assumption, not a contractual calculation. A rent review, lease formula, provider terms or property-specific change can alter the amount.
For additional mortgage borrowing, the tool treats the amount needed after entered cash as a separate repayment mortgage at the rate and term you select. It does not refinance your current mortgage or predict a lender’s offer. Ask the lender whether it will approve the additional borrowing and whether the existing mortgage rate or term would change.
One-off costs and affordability
Buying an initial share or staircasing can involve a deposit, solicitor’s fees, valuation costs, mortgage fees, landlord administration fees and possible Stamp Duty Land Tax. The amount depends on the transaction and your lease. Use a solicitor’s and lender’s figures rather than including an assumed fee in a monthly projection.
The lender or scheme provider completes its own affordability assessment. The planner does not test income, credit history, building condition or whether a home is suitable. It also does not model house-price changes, repairs, insurance increases or future rent reviews. Stress-test the total with a higher mortgage rate and higher charges before making a decision.
A practical checklist
- Confirm the current full-home valuation and share percentage in your lease.
- Record the actual mortgage payment, rent and each recurring charge separately.
- Ask the landlord for the permitted staircasing sizes, current valuation process and any rent recalculation.
- Ask the lender how extra borrowing changes the mortgage, rate and term.
- Add valuation, legal, lender and administration costs as one-off cash needs.
- Replace the planner’s proportional rent estimate with the new lease or offer figure before committing.
This guide uses GOV.UK Shared Ownership and Right to Shared Ownership guidance for England. Scheme terms vary by provider, funding programme and lease; Scotland, Wales and Northern Ireland have separate arrangements. Confirm the applicable rules with your landlord, lender and solicitor.