More than one in five homes in England and Wales are held leasehold rather than freehold — 3.72 million titles — and the share climbs to almost every flat: 97.7% of flats sold in 2025 were leasehold (HM Land Registry price-paid data, standard sales). Millions of those leaseholders will, at some point, pay to extend their lease. A common worry among the ones who also own a second property — a buy-to-let, an inherited house, a holiday flat — is whether extending will trip the 5% additional-property stamp duty surcharge.
On the way the rules are written, it does not. Here is why, and what stamp duty (if any) actually applies.
How the additional-property surcharge works
The higher rates of Stamp Duty Land Tax (SDLT) — the additional-property, or "second home", surcharge — add a flat 5% to the standard bill when you buy a residential property and, at the end of the day the purchase completes, you own two or more dwellings and are not replacing your only or main residence (Finance Act 2003, Schedule 4ZA). The rate rose from 3% to 5% on 31 October 2024 (HMRC).
The word that does the work is dwelling. The surcharge is triggered by acquiring an additional dwelling, and it is a flat 5% of the whole price — no nil-rate band, no taper, no ceiling:
| Purchase price | Standard SDLT | With 5% surcharge | Surcharge portion |
|---|---|---|---|
| £150,000 | £500 | £8,000 | £7,500 |
| £250,000 | £2,500 | £15,000 | £12,500 |
| £300,000 | £5,000 | £20,000 | £15,000 |
| £500,000 | £15,000 | £40,000 | £25,000 |
Figures from the Homecost stamp duty calculator, England, 18 August 2026.
Why extending your own lease is different
Extending the lease on a flat you already own does not add a dwelling to your name. You already owned that flat; a lease extension simply lengthens the interest you hold in it. In the counting test that drives the surcharge, the number of dwellings you own before and after the extension is the same.
That is the whole point. Schedule 4ZA asks how many dwellings you end up owning. Buying a new flat while keeping an old one takes you from one dwelling to two — the surcharge bites. Extending the lease on a flat you already hold leaves the count unchanged — so the transaction is not a "higher rates transaction", whether or not you happen to own other property elsewhere.
This holds for both routes to a longer lease:
- The statutory route — under the Leasehold Reform, Housing and Urban Development Act 1993, a qualifying flat leaseholder can require the freeholder to grant a 90-year extension at a "peppercorn" (effectively nil) ground rent.
- The informal route — a negotiated extension agreed directly with the freeholder, on whatever terms the two sides settle.
Either way, you are deepening an interest in a home you already own, not buying an additional one. (The government has legislated to reform the statutory terms through the Leasehold and Freehold Reform Act 2024; provisions are being brought into force in stages, per gov.uk.)
What stamp duty does apply to an extension
A lease extension can still be a chargeable transaction — but on the premium you pay for it, at standard rates, with no surcharge. Two thresholds decide whether anything is due or reportable:
- Below a £40,000 premium: no SDLT return is required (HMRC).
- £40,000 to £125,000 premium: a return is due, but the standard rate across the first £125,000 is 0%, so the tax is nil.
- Above a £125,000 premium: standard rates apply to the slice above £125,000 (2% to £250,000, 5% above) — but still no 5% surcharge.
On the statutory route the new lease carries a peppercorn rent, so there is no "net present value of rent" charge — only the premium counts. An informal extension that keeps or raises a ground rent can bring the rent into the calculation; the full SDLT mechanics of a surrender-and-regrant lease extension are set out separately.
The contrast is stark. Buying a £150,000 second home costs £8,000 in SDLT. Paying a £150,000 premium to extend the lease on a flat you already own costs £500 — the same headline figure, taxed as a premium at standard rates rather than as an additional dwelling.
(Extension premiums are set by valuation and negotiation. The figures above illustrate how the tax is calculated, not what any particular extension is worth.)
The edge cases
A few situations change the picture, and each turns on whether a separate dwelling is being acquired:
- Buying the freehold at the same time. Flat owners who club together to buy the freehold of their block (collective enfranchisement) are acquiring a further interest, not additional dwellings — but where a block contains separate flats or commercial units, the analysis is handled property by property.
- Extending as part of buying the flat. If a lease extension is bundled into the purchase of the flat itself, the purchase is the transaction that counts, and the surcharge follows the normal rules for that purchase.
- Company or trust ownership. Different rules apply where a company or trust holds the lease.
None of these is a loophole; they are reminders that the surcharge follows the dwelling, not the paperwork.
The bottom line
The additional-property surcharge is designed to catch the acquisition of an extra home. A lease extension is not that — it is a longer hold on a home you already own — so extending does not trigger the 5% charge, even for a leaseholder who owns other property. Any stamp duty is charged on the premium at standard rates, and most extensions fall below the point where a bill arises at all.
You can see how the surcharge stacks against the standard bill for any price on the Homecost stamp duty calculator, and check the true monthly cost of any leasehold flat — try a Docklands postcode such as E14 9GE — on the main tool. For more on the upfront and running costs of buying, browse the cost intelligence guides.
This is general information about how the rules work, not advice, and it does not value any individual lease or extension. A conveyancer confirms the position on your own facts. Speak to a qualified adviser before acting.