In brief
- Treat all-in completion cash as the core decision metric, not tax in isolation.
- Buyer type and nation can shift costs materially at the same property price.
- Run at least three scenarios before setting your offer ceiling.
- Confirm final treatment with official sources and your conveyancer.
Definition in plain English
If you buy a new main home before selling your previous one, you pay the 5% SDLT additional dwelling surcharge at completion — because you temporarily own two properties. You can reclaim the full surcharge from HMRC once you sell the previous main residence, as long as you do so within 36 months. The refund claim must be made within 12 months of the sale (or 12 months from the original SDLT filing deadline, if later).
Context
This refund mechanism is important for buyers who cannot synchronise the sale of their existing home and the purchase of their new one on the same day. Understanding the 36-month window and the refund claim process removes a key source of confusion about whether the surcharge applies to standard home-movers.
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Worked examples (home mover, typical fees)
When the surcharge applies to a home move
The 5% additional dwelling surcharge applies at completion if you already own another residential property at that point. For most home-movers who sell their existing property on the same day they buy the new one, the surcharge does not apply — there is no moment at which they own two homes simultaneously. In a simultaneous sale and purchase, standard SDLT rates apply.
However, many transactions in a chain do not complete simultaneously. A buyer may complete on the purchase of their new home one or two days before the sale of their existing home completes — or, more commonly, a buyer purchases before they have found a buyer for their existing property, or while their existing sale has fallen through. In these cases, at the moment of completing the new purchase, the buyer owns two properties and the surcharge applies.
The surcharge also applies if you buy a new main residence and intend to sell the old one but have not yet done so at the time of completing. Your solicitor will advise you to pay the surcharge at completion and claim a refund once the old property is sold — provided you do so within the 36-month window.
How to claim the surcharge refund
The refund process involves writing to HMRC's SDLT office after the sale of the previous main residence has completed. The claim should include: the SDLT unique transaction reference number (UTR) from the original purchase; details of the old property (address, title number); details of the sale (completion date, sale price); and your contact details. HMRC will verify that the conditions are met and refund the surcharge — which is 5% of the original purchase price — by bank transfer.
Your solicitor can assist with the refund claim, though many firms charge a fee for this post-completion service. It is straightforward enough that some buyers handle it directly, using HMRC's online amendment service or by writing to HMRC. Always keep the original SDLT completion pack, which your solicitor should provide after the original transaction.
Refunds are typically processed within 15 working days of HMRC receiving a valid claim. If the claim is delayed or rejected, you can appeal to the First-tier Tribunal (Tax).
Cash planning when the surcharge applies
The practical implication for home-movers who cannot synchronise is that they need significantly more cash at completion of the new purchase. On a £500,000 new home, the standard SDLT is approximately £12,500; with the 5% surcharge, the total rises to approximately £37,500 — a £25,000 additional cash requirement at completion.
This additional £25,000 is recoverable once the old home sells, but you need the cash available at the point of completing the purchase. If your sale proceeds are being used to fund the purchase (which is the typical arrangement in a chain), and the sale is completing simultaneously, the surcharge does not apply. The problem arises when the timings diverge.
Budget conservatively: if there is any possibility that your sale and purchase will not complete simultaneously, model the completion budget using the additional property SDLT setting and maintain cash reserves to cover it. If the transactions do complete simultaneously, your solicitor will apply standard SDLT rates and the extra reserves simply remain in place.
Decision framework used by careful buyers
Start with an offer ceiling based on total cash, not headline house price. In practice, buyers who only track deposit and mortgage payments can miss the transaction-cost layer, which is exactly where completions become stressful.
Use a three-pass approach: first estimate tax by nation and buyer type, then add realistic fees, then pressure-test the result by increasing the offer by £10,000 and £25,000. This shows how sensitive your budget is before bidding.
Treat the model as a planning instrument. Final legal liability always sits with official calculators and your conveyancer’s completion statement, but early visibility reduces avoidable surprises.
Practical checklist before making an offer
Confirm your likely buyer status first (home mover, first-time buyer, or additional property). Switching status can alter tax materially at the same price point, so this should be fixed before negotiating.
Collect at least two conveyancing quotes and check what is included. Buyers often compare legal fees without checking disbursements, search packages, leasehold supplements or transfer fees.
Keep a contingency buffer instead of budgeting to the exact minimum. A modest reserve can protect timelines when valuation, legal or lender admin costs move late in the process.
Frequently asked questions
Do I pay the second home surcharge when moving house?
Only if you own your old home at the moment your new purchase completes. If sale and purchase complete simultaneously (common in chains), you do not pay the surcharge — standard rates apply. If you complete the purchase before your sale completes, you temporarily own two properties and must pay the surcharge, but you can reclaim it after selling within 36 months.
How long do I have to sell my old home to get the surcharge refund?
36 months from the completion date of the new purchase. If you sell within 36 months, you can reclaim the full 5% surcharge. If the old property is not sold within 36 months, the right to a refund is permanently lost.
How do I claim the stamp duty surcharge refund?
By contacting HMRC after the old home has been sold. You can submit an amended SDLT1 return online via HMRC's SDLT portal or write to HMRC's Stamp Duty Land Tax office. You will need the original SDLT unique transaction reference and details of both transactions. Claims must be made within 12 months of the sale of the previous main home.
What if my sale falls through — do I still have to pay the surcharge?
If your purchase completes while you still own the old home (even if your sale has fallen through), the surcharge applies at completion. You can still claim the refund if you subsequently sell the old home within 36 months of your purchase. In the meantime, you will need the surcharge funds available at completion.
Does the 36-month clock start from exchange or completion?
From completion of the new purchase — the date you legally take ownership. Exchange creates a binding contract but does not transfer title. The 36-month window runs from the completion date, not the exchange date.
Can the refund be claimed if I sell to a family member?
Yes, provided the sale is at market value and represents a genuine disposal of the property. Selling at a significant undervalue to a connected person may cause HMRC to scrutinise the transaction. Your solicitor will advise on this if the sale circumstances are unusual.
How much is the refund on a typical home purchase?
The refund is 5% of the purchase price of the new home. On a £400,000 purchase, the surcharge was £20,000 (5% × £400,000) and the full £20,000 is refunded once the old home is sold within 36 months. The refund is in addition to any standard SDLT paid, which is not refunded.
References
- GOV.UK: Stamp Duty Land Tax — Primary SDLT rates and process guidance.
- Revenue Scotland: LBTT — Official LBTT rates and ADS information.
- Welsh Revenue Authority: LTT — Official LTT rates and higher-rate guidance.
- GOV.UK: SDLT refunds for previous main residence — Refund windows and conditions.
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