Shared Ownership vs Outright Purchase: Total Cost Comparison
Including stamp duty, rent on the unowned share, and staircasing costs. See the full picture over 5, 10, and 25 years.
Key Takeaways
- •Shared ownership: SDLT on initial share only, no further SDLT until ownership crosses 80%
- •Market value election: pay SDLT on full value upfront — no SDLT on any future staircasing
- •Income cap: £80,000/year (£90,000 in London)
- •Initial share: 10–75%. You pay rent on the housing association's share (typically 2.75–3% p.a.)
- •FTB relief applies to your initial share purchase
In this article
Two SDLT Options: Staged vs Market Value Election
Unlike a standard purchase, shared ownership buyers have a choice of two SDLT approaches. This election is irrevocable — you must decide at the time of purchase.
Option 1: Staged SDLT
Pay SDLT only on the lease premium (your initial share). No further SDLT on staircasing until your cumulative ownership crosses the 80% threshold. Once you cross 80%, SDLT becomes due on the full market value at that point.
- Lower upfront SDLT cost
- Good if staircasing slowly
- SDLT shock when crossing 80%
- Property price rises = higher future SDLT
Option 2: Market Value Election
Pay SDLT on the full market value of the property upfront, as if you were buying it outright. No further SDLT on any subsequent staircasing, regardless of how many tranches you buy or when.
- Zero SDLT on all staircasing
- Certainty of total SDLT cost
- Higher upfront payment
- Wasted if you sell before staircasing much
Example: £250,000 Property, 25% Initial Share
Staged: SDLT on £62,500 share. As FTB under £300k = £0 upfront. SDLT due when crossing 80% at future market value.
Market value election: SDLT on £250,000. As FTB under £300k = £0 upfront. No SDLT ever on staircasing.
In this case both options cost £0 upfront — the election only matters if the market value exceeds £300,000.
Total Cost Comparison Tool
Adjust the property value, your initial share percentage, and the annual rent rate on the housing association's share to see your SDLT options and monthly rent cost. FTB rates applied automatically.
Cost Comparison Tool
Your share price
£62,500
Monthly rent on HA share
£430/mo
£5,156/year
SDLT options
Staged: £0
Market value: £0
Outright FTB: £0
Rent rate typically 2.75–3% of the HA share's value per year. This does not include service charges (typically £100–£300/month for new builds).
£250,000 Property: 5, 10, 25-Year Cost Comparison
The table below compares cumulative total costs for three scenarios on a £250,000 property: 25% shared ownership share, 50% shared ownership share, and outright purchase. Assumptions: 5% annual house price growth, 2.75% annual rent on unowned share, 5% mortgage rate, FTB SDLT rates applied.
| Cost Element | SO 25% Share | SO 50% Share | Outright FTB |
|---|---|---|---|
| At Purchase | |||
| Purchase price (your share) | £62,500 | £125,000 | £250,000 |
| Initial SDLT (staged) | £0 | £0 | £0 |
| Deposit needed (5%) | £3,125 | £6,250 | £12,500 |
| Annual running costs | |||
| Monthly mortgage (95% LTV) | ~£295/mo | ~£590/mo | ~£1,176/mo |
| Monthly rent on HA share (2.75%) | ~£430/mo | ~£286/mo | £0 |
| Total monthly housing cost | ~£725/mo | ~£876/mo | ~£1,176/mo |
| Cumulative total cost (excluding price appreciation) | |||
| 5 years total paid | ~£43,500 | ~£52,560 | ~£70,560 |
| 10 years total paid | ~£87,000 | ~£105,120 | ~£141,120 |
Indicative figures only. Assumes 25-year capital repayment mortgage at 5%, 2.75% annual rent on HA share, no staircasing or price changes modelled in base case. Actual costs will vary. Consult a mortgage broker for personalised figures.
Staircasing and the 80% SDLT Threshold
Staircasing means buying additional tranches of your property from the housing association. Under the 2021 shared ownership model, you can staircase in increments as small as 1%. The critical SDLT threshold sits at 80%.
The 80% Threshold Rule (Staged Option)
If you chose the staged SDLT option at purchase, you pay no SDLT on each staircasing tranche until your total ownership reaches or exceeds 80%. The first staircasing transaction that takes you over 80% triggers a "final staircasing charge" — SDLT on the full market value at that point, less the SDLT already paid on earlier tranches.
Example: You bought 25% at £250,000 (£0 SDLT). 5 years later the property is worth £320,000. You staircase to 85%. SDLT is now due on £320,000 full value. FTB rates: £320,000 → 5% × £20,000 = £1,000. Less previously paid £0. You owe £1,000 SDLT.
Planning to staircase rapidly? The market value election at purchase locks in SDLT at today's price and eliminates the 80% threshold risk entirely. Each staircasing transaction also costs solicitor fees (typically £750–£1,500) — budget these separately. See our FTB stamp duty calculator to model different property values.
Should You Elect Market Value for SDLT?
The decision depends primarily on your staircasing intentions and expectations about property price growth:
| Your situation | Elect market value? | Reason |
|---|---|---|
| Plan to staircase to 100% within 5 years | Yes | Lock in current value; save SDLT as prices rise |
| Buying small share (10–25%), uncertain about staircasing | No | Upfront SDLT on full value not justified |
| Property near £300k FTB threshold | Consider | Market value SDLT may still be £0 or minimal |
| Property well over £300k threshold | Depends | Model both options with solicitor before deciding |
| Strong house price growth expected | Yes | Future market value SDLT will be higher |
Always obtain written advice from a solicitor specialising in shared ownership before making the election. The decision is irrevocable and a mistake could cost thousands. Model both scenarios using actual numbers from your specific property.
Eligibility: Income Caps and Criteria
Shared ownership has eligibility requirements that outright purchases do not. Key criteria:
- Income cap: Household income must be no more than £80,000 per year (£90,000 in London). Above this, you do not qualify for shared ownership under most housing association schemes.
- Cannot afford outright: You must be unable to afford to buy a home suitable for your needs on the open market. This is a self-assessment criterion applied by housing associations.
- First-time buyer or specific circumstances: Priority is given to first-time buyers. Existing homeowners must be selling their current home and must prove they cannot afford an equivalent property outright in the area.
- Leasehold-only: Shared ownership properties are always leasehold. Lease length is crucial — short leases (under 80 years) make selling and mortgaging extremely difficult. Always check remaining lease length before buying.
- Right of first refusal: When you want to sell, the housing association has an 8-week right of first refusal to find a buyer themselves. This can slow the sale process compared to an open-market sale.
Ready to see your numbers?
Use our free calculator to see exactly how much stamp duty you need to budget for.
Check your first-time buyer savings
Emma Richardson, MRICS
Chartered Surveyor & Property Tax Specialist
Emma Richardson is a RICS-qualified Chartered Surveyor with over 12 years of experience in UK property taxation. She founded Stamp Duty Calculator to help buyers understand the complex world of property transaction taxes.