Shared Ownership Calculator

Shared ownership lets you buy a share of a property (between 25% and 75%) and pay rent on the remaining share owned by a housing association. You need a mortgage only for the share you buy, plus a deposit on that share (typically 5-10% of the share value). This dramatically reduces the upfront cost compared to buying outright.

Monthly costs include your mortgage payment on the purchased share, rent to the housing association on the unowned share (typically 2.75% of its value per year), service charges and any ground rent. The rent portion usually increases annually by CPI + 1%, though newer leases may cap increases at CPI only.

This calculator breaks down all monthly costs for a shared ownership purchase. Enter the property value, the share you are buying, your deposit and the interest rate to see a full monthly cost comparison against renting or buying the whole property with a larger mortgage.

How Shared Ownership works. Buy 25-75% of a property (the 'share'), pay rent on the remaining percentage to a housing association at ~2.75-3% of unsold equity. £300,000 property, buy 50%: mortgage on £150,000 + rent on £150,000 at 2.75% = £344/month rent. Mortgage on £150k at 5% over 25 years = £877/month. Total housing cost = £1,221/month — substantially less than buying 100% at £1,754/month, but you only own 50% of capital appreciation.

Staircasing — buying more of your home. After living in your shared-owned property for a period (usually 1+ year), you can 'staircase' — buy additional shares (typically minimum 10% per transaction). New 1% Staircasing model (since 2021) allows annual 1% purchases at fixed RPI-linked valuations. Eventually you can own 100% (in most properties) — exception: 'protected areas' (rural/coastal) where staircasing is capped at 80%. Each staircasing transaction has SDLT, legal fees, and valuation costs.

Eligibility and the 80k income cap. To qualify in 2026/27: household income under £80,000 (£90,000 London); cannot afford to buy a comparable home outright; first-time buyer OR existing shared owner staircasing OR home mover unable to afford full-purchase property. Some properties prioritise local connection or key worker status. Apply via the local Help to Buy agent for your region. Limited supply — properties typically allocated within weeks of release.

Major risks and pitfalls. (1) You're still 100% responsible for repairs and maintenance, even on the share you don't own; (2) Rent increases annually (typically RPI + 0.5%) — much faster than mortgage payments; (3) Service charges can be high (£200-£500/month for new builds); (4) Resale is often restricted — must offer back to housing association first; (5) Lender market is narrow — fewer mortgage products for SO buyers, often higher rates; (6) Leasehold structure means ground rent and potential reform risk. Always read the lease carefully.