Shared Ownership Staircasing — Stamp Duty and Costs Explained 2026/27
How buying additional shares in a shared ownership home (staircasing) is taxed for stamp duty purposes, and the other costs involved in 2026/27.
The Market Value Election Decision
At the point of an original shared ownership purchase, buyers can choose to pay Stamp Duty Land Tax calculated on the full market value of the property (a market value election) rather than just on the initial share purchased. This costs more upfront but generally removes SDLT liability on any future staircasing purchases as you buy further shares, right up to full ownership. Buyers who don't make this election pay SDLT only on their initial share at the outset, but may face further SDLT charges as staircasing purchases push their total share past certain value thresholds — the right choice depends partly on how likely and how soon you expect to staircase further.
Staircasing Increments and Lease Terms
| Feature | Typical arrangement |
|---|---|
| Minimum staircasing increment | Often 5% or 10%, though some schemes allow smaller steps (e.g. 1%) |
| Valuation for staircasing | An independent RICS valuation is usually required to set the price of the new share |
| Funding the purchase | Extending your existing mortgage, remortgaging, or using savings |
| Rent | Charged on the landlord's remaining share, typically reducing as you staircase |
Because each staircasing purchase is usually based on a fresh, independent valuation of the property at that time rather than the original purchase price, the cost per percentage point can rise or fall with local property values between staircasing events — buying a further 10% share when prices have risen since your last purchase costs more per percentage point than it would have earlier.
Funding a Staircasing Purchase
Most shared ownership lenders will extend an existing mortgage to fund a staircasing purchase, subject to a fresh affordability assessment reflecting your current income and outgoings. Where your existing lender doesn't offer further advances for staircasing, or a better rate is available, remortgaging to a new lender at the point of staircasing is also an option, though it brings the usual remortgage costs and paperwork into what would otherwise be a more straightforward transaction with your existing lender.
Rent as Your Share Grows
Rent under a shared ownership lease is charged on the landlord's remaining share of the property, so as your owned percentage increases through staircasing, the rent payable typically falls in step, reaching zero once you've staircased to 100% ownership and the property becomes yours outright (subject to any ground rent or service charge that may continue to apply depending on the lease and building type).
Before You Staircase
- Check whether a market value election was made at your original purchase, and what that means for SDLT on this staircasing purchase
- Confirm the minimum increment allowed under your specific lease
- Get an independent valuation to understand the current cost per percentage point
- Compare extending your existing mortgage against remortgaging to fund the purchase
Use the shared ownership calculator below to model the cost of your current share, and the stamp duty calculator to check any SDLT due on a staircasing purchase.
Frequently asked questions
Do I pay stamp duty every time I staircase to buy a bigger share?
Shared ownership buyers can elect to pay all the stamp duty due upfront, calculated on the full market value of the property (a 'market value election'), which means no further SDLT is due on future staircasing purchases up to 100% ownership. Without that election, SDLT can become due again as your share increases past certain thresholds, so the election is worth understanding carefully at the point of the original purchase.
Is there a minimum share I have to buy each time I staircase?
Many shared ownership leases set a minimum increment for staircasing purchases (commonly 5% or 10%), though some newer models allow smaller, more frequent increments of as little as 1%. The specific lease terms for your property set the actual minimum, so it's worth checking your lease rather than assuming a standard figure applies.
Do I need a new mortgage or can I extend my existing one when staircasing?
Most lenders can extend your existing mortgage to fund a staircasing purchase, or you may choose to remortgage at that point if a better rate is available or your existing lender doesn't support further advances for staircasing. Either way, a fresh affordability assessment is generally required for the additional borrowing.
Do rent payments reduce as I staircase?
Yes — rent on a shared ownership property is charged on the landlord's remaining share, so rent typically reduces (often roughly proportionally) as your owned share increases through staircasing, until it eventually reaches zero once you own 100%.
Try the calculators
Related reading
Shared Ownership Staircasing: A Complete 2026 Guide
How shared ownership staircasing works in 2026: costs, valuations, mortgage steps, stamp duty traps and whether buying more shares is worth it.
Shared Ownership 2026: How Staircasing Works and the Hidden Costs (Part 11)
Shared ownership UK 2026: buying 25–75% of a home, how staircasing works, SDLT on every purchase, service charges, lease extension costs, resale restrictions, and when it actually makes financial sense.
Downsizing in Retirement — The Stamp Duty and Pension Maths for 2026/27
How stamp duty, state pension timing and releasing equity interact when downsizing your home in retirement, for the UK 2026/27 tax year.