Staircasing Stamp Duty Calculator
Calculate SDLT on additional shared ownership shares bought after your initial purchase. Handles the 80% threshold rule, linked transactions, and lets you stress-test a sequence of future tranches.
SDLT Payable
£0
New Total Ownership: 35%
Consideration
£25,000
Share Being Purchased
10%
Below 80% threshold — SDLT is on the price paid for the share only.
Which calculator do I need?
Shared ownership has two distinct SDLT moments. Each has its own calculator.
| Your situation | Use this | What it does |
|---|---|---|
| Buying my first share of a shared ownership home | Shared Ownership Calculator | Compares the market value election against paying SDLT only on the initial share. Includes FTB relief. |
| Already a shared owner, buying more shares (staircasing) | Staircasing Calculator You are here | Calculates SDLT on each additional tranche, flags the 80% threshold, and applies the linked transactions rule when you cross it. |
| Staircasing in a single jump to 100% ownership | Either works — start here, then see the final staircasing guide | A single transaction crossing 80% and reaching 100% triggers one linked-transaction SDLT calculation, covered here. |
Quick rule of thumb: if you have not yet completed your initial shared ownership purchase, you are on the wrong page — use the shared ownership calculator instead. The staircasing calculator is for the second purchase onwards.
How staircasing SDLT works
Under the default staircasing election (the one you ended up with if you did not tick “market value election” on your SDLT1 at initial purchase), HMRC sets out a very specific rule for further SDLT on additional share purchases. GOV.UK guidance is unambiguous: “If you buy more shares in a property... until your share reaches more than 80%, you don’t pay any more SDLT or tell HMRC about the transactions in a SDLT return.”
Cumulative share ≤ 80%
No further SDLT on staircasing tranches. No SDLT return required. Buy as many additional shares as you like, in any size, with zero SDLT impact.
The transaction that crosses 80%
This tranche is treated as linked with every earlier staircasing purchase. SDLT is calculated on the cumulative consideration paid for all linked share purchases.
Every tranche after 80%
Each subsequent staircasing transaction is also linked. SDLT is recalculated on the new cumulative total, with SDLT already paid credited against the new liability.
SDLT is calculated on consideration, not market value
After crossing 80%, the linked-transaction calculation uses the actual cumulative consideration paid for the share purchases, applied to standard SDLT rate bands. It is not a market value re-rating, and it does not rewrite the SDLT originally paid on your initial share premium.
2026 SDLT rate bands applied to staircasing
When SDLT does become payable on a staircasing transaction (only after crossing 80% under the staircasing election), the calculator applies the current residential SDLT bands to the cumulative linked consideration. These are the bands in force from 1 April 2025:
| Portion of consideration | Standard rate | With ADS (additional property) |
|---|---|---|
| Up to £125,000 | 0% | 5% |
| £125,001 – £250,000 | 2% | 7% |
| £250,001 – £925,000 | 5% | 10% |
| £925,001 – £1.5m | 10% | 15% |
| Above £1.5m | 12% | 17% |
Bands per GOV.UK SDLT rates. The 5% additional dwelling surcharge applies if you already own another property anywhere in the world at the effective date of the staircasing transaction.
Worked examples
Three scenarios on a property worth £400,000 at the time of each staircasing transaction. All assume the default staircasing election (no market value election made at initial purchase), no additional property surcharge, no FTB relief.
| Scenario | Current share | Buying | New cumulative | Consideration | SDLT on this tranche |
|---|---|---|---|---|---|
A. Below 80% Routine staircasing tranche | 40% | +25% | 65% | £100,000 | £0 |
B. Crossing 80% Trigger transaction — all prior staircasing tranches now linked | 65% | +25% | 90% | £100,000 | £1,500 on £200k linked total |
C. After 80% Final staircasing to 100% | 90% | +10% | 100% | £40,000 | £2,300 recomputed on £240k linked total, less SDLT already paid |
How scenario B works: the 80%-crossing tranche is linked with the first £100k staircasing purchase, giving cumulative consideration of £200,000. Standard SDLT on £200,000 is £1,500 (0% on the first £125k, 2% on the next £75k). The initial share premium is treated separately and not pulled into this linked group.
How scenario C works: the new tranche is linked with the previous two staircasing transactions, giving £240,000 cumulative. SDLT on £240,000 is £2,300 (0% / 2%). SDLT already paid on the 80%-crossing transaction (£1,500) is credited. Net additional SDLT due: £800 — not the £2,300 shown in the table, which is the gross linked-total figure before credit. The calculator does this credit step automatically.
When should you staircase?
Going straight to 100%
A single staircasing transaction from your current share to 100% triggers exactly one SDLT calculation under the linked-transactions rule. This is often the simplest path: one valuation, one solicitor instruction, one SDLT return. See the final staircasing guide for the legal mechanics.
Staircasing in stages
Multiple tranches under 80% are SDLT-free, but each one over 80% is a separate linked-transaction recalculation with its own SDLT return and 14-day deadline. If you plan to staircase beyond 80%, sequencing each step matters — use the calculator to model a 2-step plan vs a 3-step plan.
Holding below 80%
If you stay at or below 80%, you never trigger any further SDLT under the staircasing election. Some owners stair-case to a comfortable level (e.g. 75%) and stop — the trade-off is rent on the remaining share vs the SDLT savings from never crossing the threshold.
Rising property value
Each tranche is priced on a current RICS valuation. If the property value is rising, the same percentage costs more each time. The calculator lets you model different future valuations to see how price movement changes the SDLT cost of a 2025 vs 2027 staircasing decision.
Frequently asked questions
Do you pay stamp duty when staircasing?
Only sometimes. If you made a market value election at your initial shared ownership purchase, no SDLT is ever due on staircasing. Under the default staircasing election, tranches that keep your cumulative ownership at 80% or below do not require any further SDLT or SDLT return. SDLT re-engages on the transaction that takes you above 80%, and that transaction is linked with all earlier and subsequent staircasing tranches.
How is this calculator different from the shared ownership calculator?
The shared ownership calculator is for your initial purchase: it compares the market value election against paying SDLT only on the first share you buy. This staircasing calculator is for what comes next: buying additional shares from the housing association after that initial purchase. It handles the 80% threshold rule and the linked-transactions calculation that the initial-purchase calculator does not need to consider.
What is the 80% threshold in shared ownership staircasing?
The 80% threshold is the point at which SDLT rules change under the staircasing election. While your cumulative ownership stays at 80% or below, no further SDLT is due on staircasing tranches. The transaction that takes you above 80% is the trigger: it, along with every earlier staircasing purchase, is treated as linked under FA 2003, and SDLT is calculated on the cumulative consideration paid for all those linked share purchases.
Does the calculator handle the linked transactions rule after 80%?
Yes. Once a staircasing transaction crosses the 80% line, the calculator treats it and all prior staircasing tranches as linked, sums the cumulative consideration, applies the standard SDLT rate bands to that total, and credits SDLT already paid on the initial share premium. Every staircasing transaction after the 80% crossing is also recalculated against the updated cumulative total.
What share size should I use in the calculator?
Enter the additional share you are buying as a percentage of the full property, not as a percentage of the housing association share. For example, if you currently own 40% and are buying another 20%, enter 20%. Use a current RICS valuation for the full property value, because each staircasing purchase is priced on the market value at the time of the transaction, not the value when you first bought your share.
Does first-time buyer relief apply to staircasing?
First-time buyer relief is only available at the initial purchase, not on staircasing. If you claimed FTB relief on your initial share, you have already used the relief. Staircasing tranches are assessed on the consideration paid for the additional share using standard SDLT rate bands, with no FTB carve-out, regardless of whether your initial purchase qualified for relief.
Is staircasing notifiable to HMRC?
No while your cumulative ownership stays at 80% or below: HMRC specifically excludes those staircasing tranches from the SDLT return requirement. Yes once a transaction takes you above 80%, and on every staircasing transaction afterwards. Notifiable transactions require an SDLT1 return filed within 14 days of the effective date, usually handled by your solicitor.
Reviewed by
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 Calculate My Stamp Duty UK to help buyers understand the complex world of property transaction taxes.