Staircasing Stamp Duty: Additional Share Purchases
How SDLT works on each staircasing transaction, the 80% threshold rule, and worked examples at different property values.
Key Takeaways
- Staircasing SDLT rules here only apply if you chose the default pay-in-stages option at initial purchase, because the market value election eliminates all future staircasing SDLT
- While your cumulative ownership stays at 80% or below, HMRC does not require any further SDLT payments or SDLT returns on staircasing tranches, regardless of the amount paid
- The transaction that takes you over 80% is the trigger: it, together with all earlier and subsequent staircasing purchases, is treated as linked under FA 2003 and SDLT is calculated on the cumulative consideration actually paid for those shares
- SDLT on the 80% crossing is NOT calculated on the current market value of the property; it is calculated on the total consideration paid for all linked share purchases using the standard rate bands
- Once the 80% line has been crossed, every subsequent staircasing transaction is also linked, with SDLT recalculated on the new cumulative consideration and previously paid SDLT credited
- The consideration for each individual staircasing purchase is based on a current RICS valuation of the whole property at that time
- Returns are only required at the point you cross 80% and on any subsequent linked staircasing transactions, not on tranches that keep you at or below 80%
- Jumping directly to 100% in one transaction is the simplest path and avoids the linked-transaction mechanics entirely for later purchases
In this article
What Is Staircasing?
Staircasing is the process of buying additional equity in your shared ownership property from the housing association. When you initially bought your share (say 40%), the lease granted you the right to purchase more shares over time. Each time you buy an additional percentage, you are staircasing. You can staircase as many times as you like (subject to your lease terms) until you reach 100% ownership.
The price you pay for each additional share is based on the current open market value of the property at the time of that specific staircasing transaction. If your property has increased in value since you first bought, you will pay more per percentage point than you did initially. This is why property value growth affects the total SDLT liability under the staircasing election.
For context on how your initial election affects whether you pay SDLT at all on staircasing, see the market value election guide. If you made the market value election at your initial purchase, you pay no SDLT on any staircasing transaction, full stop. The rules on this page apply where you did not make the market value election, ie. you are using the default pay-in-stages option.
When SDLT Applies on Staircasing
Under the default pay-in-stages option, HMRC sets a very specific rule for further SDLT obligations on staircasing tranches. Per GOV.UK guidance: “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.”
In other words, there is no further SDLT and no SDLT return required while your total ownership remains at 80% or below, no matter how large each staircasing tranche is. The SDLT system only re-engages when a transaction takes your cumulative ownership over 80%.
Cumulative Ownership At or Below 80%
No further SDLT, no return required. HMRC is not concerned with staircasing tranches at this stage.
Zero SDLT, zero filings up to the 80% line
Crossing Over 80%
The transaction that takes you over 80% is treated as linked with all previous staircasing purchases. SDLT is recalculated on the cumulative consideration paid.
Linked transactions: cumulative consideration, not market value
Staircasing Below and Up To 80%
While your total ownership stays at 80% or below after a staircasing tranche, no SDLT is due and no SDLT return is required for that transaction. This is a feature of the shared ownership SDLT regime, not a function of the rate bands: even if you bought a single tranche worth £400,000, you would still owe nothing at that point, because you have not yet crossed the 80% line.
The price you pay for each tranche is still based on a current RICS valuation of the whole property. The housing association calculates the share price as a percentage of that valuation. That price affects how much you pay, but it does not create a current SDLT liability until the 80% line is crossed.
Note that first-time buyer relief does not apply to staircasing purchases in any case. By the time you are staircasing, you already own a residential property (your initial share), so you are no longer a first-time buyer. When SDLT does eventually become payable on a 80% crossing, standard rates apply.
Crossing the 80% Threshold
The 80% line is the trigger point for SDLT on staircasing under the pay-in-stages option. The specific rule, set out in FA 2003 Schedule 9 and explained in the HMRC guidance, is that the transaction that takes you over 80% and all earlier and subsequent staircasing transactions are treated as linked for SDLT. SDLT on the 80% crossing transaction is calculated on the total consideration paid for all linked staircasing purchases combined with the initial share premium (the initial purchase is itself not aggregated into the linked set in this way, but the linked-transactions concept for the staircasing tranches is what matters for the new filing).
Critically, this is not a market value calculation. The SDLT is based on the cumulative consideration actually paid for the shares, not on the current open market value of the whole property. The market value basis applies only where the market value election was made at the first purchase, in which case no further SDLT arises at all.
The 80% Trigger Is a Single Transaction
If you own 70% and buy an additional 15% to take you to 85%, that 15% purchase is the transaction that crosses 80%. It is treated as linked with any prior staircasing tranche purchases, and SDLT is calculated on the cumulative consideration paid for those linked share purchases using the standard SDLT rate bands.
Linked Transactions Rule After 80%
Once the 80% line has been crossed, any further staircasing is also captured by the linked transactions rule. Each subsequent staircase requires a new SDLT calculation on the revised cumulative consideration (including the new tranche), with credit given for SDLT already paid on the earlier linked transactions. This prevents double counting.
For example, if a buyer crossed 80% by purchasing a tranche in Year 5 and paid SDLT on the total staircased consideration at that time, a later purchase in Year 7 is treated as linked. SDLT is recomputed on the new total (prior staircased consideration plus the new tranche), and the Year 5 SDLT already paid is deducted from that new total. Only the difference, if any, is payable in Year 7.
Each of these further staircasing transactions requires a new SDLT return within 14 days of the effective date. Before 80% is crossed, no returns are required at all. After 80% has been crossed, every staircasing tranche is a notifiable, linked transaction.
Example: Staircasing Below 80%
Scenario: Multiple Staircasing Tranches Keeping Ownership Under 80%
Starting ownership: 40%. Property value £400,000 at initial purchase, rising to £500,000 at the time of the final tranche shown here.
| Tranche | New Cumulative | Tranche Price | SDLT Due | Return Required? |
|---|---|---|---|---|
| +10% (property £420k) | 50% | £42,000 | £0 | No |
| +15% (property £450k) | 65% | £67,500 | £0 | No |
| +15% (property £500k) | 80% | £75,000 | £0 | No |
No SDLT is due and no SDLT return is required on any of these tranches. Per HMRC guidance, until your share exceeds 80% you do not pay any more SDLT or tell HMRC about the transactions. This is true regardless of each tranche's price.
Example: Crossing 80% in One Transaction
Scenario: Owning 70%, Buying an Extra 15% to Reach 85%
Prior staircasing purchases: 30% bought in earlier tranches (taking a buyer from a 40% initial share to 70%), with total consideration paid across those tranches of £130,000. Now buying an additional 15% at a new RICS valuation for £82,500.
| Prior linked staircasing consideration | £130,000 |
| New tranche (crosses 80%) | £82,500 |
| Total linked staircasing consideration | £212,500 |
| SDLT: 0% on £125,000 | £0 |
| SDLT: 2% on £87,500 (£125,001–£212,500) | £1,750 |
| Total SDLT payable on this crossing transaction | £1,750 |
SDLT is calculated on the cumulative £212,500 of consideration actually paid for the staircased shares, not on the market value of 85% of the property. A SDLT return is required within 14 days of the effective date of the 80% crossing transaction.
Example: Further Staircasing After 80%
Scenario: A Later Tranche Following the 80% Crossing
Continuing from the previous example: the buyer is now at 85% with prior linked staircasing consideration of £212,500 and £1,750 of SDLT already paid. Two years later they buy an additional 10% for £60,000, taking them to 95%.
| Previous linked staircasing consideration | £212,500 |
| New tranche | £60,000 |
| New total linked consideration | £272,500 |
| SDLT: 0% on £125,000 | £0 |
| SDLT: 2% on £125,000 | £2,500 |
| SDLT: 5% on £22,500 | £1,125 |
| Gross SDLT on new total | £3,625 |
| Less: SDLT already paid on 80% crossing | (£1,750) |
| Additional SDLT payable on this tranche | £1,875 |
Each post-80% tranche is a linked transaction. SDLT is recomputed on the updated cumulative consideration, with previously paid SDLT credited. A new SDLT return is required.
Filing Requirements
The filing position for staircasing under the pay-in-stages option is unusually simple. While your cumulative ownership stays at 80% or below, no SDLT return is required for staircasing transactions, no matter how large each tranche is. HMRC guidance is explicit on this point.
A return becomes required for the transaction that takes your cumulative ownership over 80%, and for every subsequent staircasing transaction (which are all linked). Each such return must be filed within 14 days of the effective date, normally completion day. Any SDLT due must accompany the return.
Your solicitor handles the SDLT return for any notifiable staircasing transaction. The Land Registry requires evidence of the SDLT filing (a SDLT certificate) before registering the updated ownership title where a return was due. Where no return is required (staircasing up to 80%), the Land Registry update proceeds on the basis of the staircasing memorandum alone.
Strategic Planning to Manage Staircasing SDLT
Under the pay-in-stages option, the shape of the 80% rule drives most planning decisions. Several strategies are worth considering:
Stop at 80% if possible: If your long-term plan is to own around 80% and no more, you will never pay any further SDLT beyond your initial share premium. Every tranche up to 80% is free of SDLT and free of any return obligation.
Go straight from below 80% to 100%: If you intend full ownership, one way to minimise SDLT complexity is to stay at or below 80% and then make a single transaction to 100%. This single linked transaction captures all the staircased consideration in one SDLT calculation with one filing.
Understand the linked transactions rule before crossing 80%: If you cross 80% in a small tranche, you still have to file and pay SDLT on the cumulative consideration of all linked staircasing tranches, not just the tranche itself. Make sure you model this before staircasing. See the final staircasing guide for how the final step to 100% fits in.
Moving to Final Staircasing
When you are ready to buy the final share and reach 100% ownership, different considerations apply. The final staircasing to 100% guide covers the SDLT calculation on that last purchase, the transition from leasehold to potential freehold, and mortgage and legal considerations specific to becoming a full owner.
For context on how the shared ownership journey fits together from start to finish, the shared ownership complete guide provides an overview of all SDLT touchpoints across the entire lifecycle.
Calculate Your Staircasing SDLT
Enter your property details to calculate the stamp duty on your staircasing transaction.
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.
Frequently Asked Questions
Do I pay stamp duty every time I staircase?
No. Under the default pay-in-stages option, you pay SDLT on your initial share premium only. No further SDLT is due and no SDLT return is required on staircasing tranches while your cumulative ownership stays at 80% or below. SDLT re-engages only if you cross the 80% line. If you made a market value election initially, no SDLT is ever due on staircasing.
What is the 80% rule in shared ownership staircasing?
Per HMRC guidance, until your share exceeds 80% you do not pay any more SDLT or tell HMRC about staircasing transactions. Once a transaction takes you over 80%, that transaction, along with the earlier and subsequent staircasing tranches, is treated as linked. SDLT is calculated on the cumulative consideration paid for all the linked share purchases, using the standard rate bands, and is not based on the current market value of the property.
Is a staircasing purchase notifiable to HMRC?
Not while your cumulative ownership is 80% or below: HMRC specifically excludes these transactions from the return requirement. Once you cross 80%, the crossing transaction and every subsequent staircasing transaction are notifiable. Your solicitor will prepare an SDLT return within 14 days of the effective date.
How is SDLT calculated when I cross 80%?
SDLT is calculated on the cumulative consideration actually paid for all the staircased shares treated as linked with the transaction that crosses 80%. Standard rate bands apply to that cumulative total. It is not a market value calculation, and it does not rewrite the SDLT originally paid on your initial share premium.
Can I staircase in large jumps to minimise SDLT filings?
Yes, subject to your lease terms. Jumping from your current share straight to 100% is called final staircasing and is covered in the final staircasing guide. This single transaction crosses 80% and reaches 100% in one step, so only one SDLT calculation and one return are needed.
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.