Buying twice from the same seller: how a later purchase rewrites the tax on the earlier one
Buy one property, then buy another from the same seller as part of the same deal, and the tax on the first purchase is recalculated. On a £400,000 house followed by a £300,000 flat the linkage costs £9,999, and £4,285 of that lands as a fresh bill on a transaction that completed months earlier. There is no time limit on how far apart the purchases can be, the deadline for the second bill is 30 days rather than 14, and the recalculation uses the rates in force when the first purchase completed.
What makes two purchases linked, and what does not
Section 108 of the Finance Act 2003 links transactions where they form part of a single plan or arrangement, or of a series of transactions, between the same vendor and purchaser or, in either case, persons connected with them. Connection takes its meaning from section 1122 of the Corporation Tax Act 2010, and it is narrower than most people assume: a relative, defined for that section by section 1123(1), means a brother, sister, ancestor or lineal descendant, which excludes cousins, aunts, uncles, nephews, nieces and unmarried partners. Connection also runs on both sides of the deal, so a husband selling one plot and his wife the adjoining one to the same buyer can produce linked transactions. Separate contracts do not help: HMRC's manual says in terms that the form in which transactions are documented will not determine whether they are linked, and separate solicitors and separate completion dates are no better. But two sales between the same parties are not automatically linked either. There must be something else connecting them, amounting to an arrangement or a series, and the practical test HMRC applies is whether the fact that the first transaction happened affected the terms of the second. A bulk discount, a price agreed across the whole package, an option granted and later exercised, or a single negotiation covering both properties will all do it. Two unconnected purchases years apart from a seller who happens to be the same person will not. There is no time limit at all on how far apart linked transactions can be, and gov.uk says so expressly.
The computation aggregates to set the rate, then apportions the tax
This is the mechanic to understand, because it explains everything that follows. Where a transaction is one of a number of linked transactions, section 55(1C) works in three steps. Step 1 applies the appropriate table to the relevant consideration. Step 2 adds the amounts together. Step 3 multiplies the result by the chargeable consideration for the particular transaction divided by the relevant consideration. And section 55(4) defines those two terms for this purpose: the relevant land is any land an interest in which is the main subject-matter of any of the linked transactions, and the relevant consideration is the total of the chargeable consideration for all of them. So the pooled price chooses the table and drives the rate, and each transaction then pays its own proportionate share of the pooled tax. Aggregation sets the rate; it does not create a single charge. Each transaction remains a separate chargeable transaction with its own effective date, its own return and its own slice. Section 108(2) permits, but does not require, a single land transaction return where linked transactions share an effective date and the purchasers are the same. HMRC will only accept one SDLT1, however, where the transactions also carry the same transaction code, where the vendors are identical too, and where they either claim no relief at all or claim the same relief; otherwise separate returns are needed. One consequence of section 55(4) catches people by surprise in both directions. Because the relevant land is any land in any of the linked transactions, a single non-residential element anywhere in the pool moves all of them onto Table B, and HMRC's manual is explicit that there is no apportionment between residential and non-residential rates in that situation. Depending on the numbers that can be a large saving or a large cost, but it is never a choice.
An illustrative example: the house, then the flat, three months later
The following figures are illustrative and not drawn from any client matter. A buyer purchases a house for GBP 400,000 to live in, and pays the standard residential rates: nothing on the first GBP 125,000, GBP 2,500 on the slice to GBP 250,000, and 5 per cent of the remaining GBP 150,000, giving GBP 7,500. Total GBP 10,000. Three months later the same seller offers the buyer a flat at GBP 300,000, and the price reflects the earlier purchase. The two are linked. The relevant consideration is now GBP 700,000. For the house, the standard table on GBP 700,000 gives GBP 25,000, apportioned by GBP 400,000 over GBP 700,000, which is GBP 14,285. The buyer has already paid GBP 10,000, so GBP 4,285 of additional tax falls due on a purchase that completed a quarter of a year ago. For the flat, which is a second dwelling and therefore attracts the higher rates, the substituted table on GBP 700,000 gives GBP 60,000, apportioned by GBP 300,000 over GBP 700,000, which is GBP 25,714. The two together come to GBP 39,999. Had the purchases been genuinely unconnected, the house would have cost GBP 10,000 and the flat GBP 20,000, a total of GBP 30,000. The linkage costs GBP 9,999, and over two fifths of that arrives as an unexpected bill on a transaction the buyer had long since filed and forgotten.
The second bill has its own deadline, and it is not fourteen days
Section 81A deals with the return on the earlier transaction, and it contains two different deadlines that are routinely conflated. Where the effect of the later transaction is that the earlier transaction becomes notifiable when it was not before, the purchaser must deliver a return within 14 days of the effective date of the later transaction. Where instead tax or additional tax becomes payable on the earlier transaction, the purchaser must deliver a further return within 30 days of the effective date of the later transaction. Finance Act 2019 cut the first of those to 14 days and left the second at 30. The public guidance describes a 14-day deadline, but that is the ordinary section 76 deadline for the later purchase itself, not the section 81A deadline for the earlier one, so do not apply one number to both. Note also that HMRC's manual says any extra tax on the earlier transaction is payable at the same time as the tax on the second, which does not sit easily with section 81A(1C), under which the tax is payable no later than the filing date for the further return. Where the two disagree the safe course is to pay within 14 days even though the further return itself is not due for 30. One further point about the recalculation: section 81A(1B) provides that any tax or additional tax payable is calculated according to the effective date of the earlier transaction, so a purchase made in 2023 and relinked by a purchase in 2026 is re-run on the 2023 rate tables for its own slice, not on today's. In practice HMRC asks you to write to Stamp Taxes quoting the unique transaction reference number for each linked transaction and setting out the revised amount.
Two thresholds of forty thousand pounds that behave differently
This is a small point that produces a disproportionate number of wrong answers, because the same figure appears in two places and only one of them aggregates. For notification, the second exception in section 77A takes an acquisition out of the requirement to file where the chargeable consideration for that acquisition, together with the chargeable consideration for any linked transactions, is less than GBP 40,000. That test is expressly pooled. For the higher rates for additional dwellings, Condition A in Schedule 4ZA asks whether the chargeable consideration for the transaction is GBP 40,000 or more, and the word linked does not appear anywhere in that Schedule. That test is not pooled. So two linked purchases of GBP 25,000 each do not become higher rates transactions by aggregation, but they do together cross the notification threshold and both must be reported. The same asymmetry runs through the higher rates generally. Whether the surcharge applies at all is decided transaction by transaction, so in a series the first purchase can sit on the standard table while the second and third sit on the substituted one, yet all three take their bands from the same pooled consideration.
Where this bites hardest, and what to ask before the second purchase
Three situations account for most of the surprises. The developer or seller offering a second and third unit at a keen price is the textbook case, because the discount is itself the evidence that the transactions form a series. An option granted and later exercised is the second, confirmed again by the First-tier Tribunal in Shinebrook Ltd v HMRC in April 2026, where the grant and the exercise were held to be two transactions and linked rather than one. The tax at stake in that case turned on other issues, but the mechanic is the point: the rate on the exercise is calculated to include the price paid on the grant, so a modest option premium taxed at nothing can still push the main purchase up a band. Third is the family arrangement, where one purchase is made by a buyer and a second by a sibling, parent or spouse from the same seller, and the parties assume that different names mean different deals. On the other side of the ledger, transactions in Scotland and Wales never link with English or Northern Irish ones, because section 108(1A) excludes them and the devolved taxes are separate, and on a straightforward exchange of properties between two people each acquisition is not linked to the other even where the parties are connected. Three questions are worth putting to your adviser before signing on a second property. Did the earlier purchase, or the prospect of this one, affect the price of either. Is the seller, or anyone connected with the seller, the same person on both. And if the answer to either is yes, what is the additional tax on the first purchase, when is it due, and who is going to file it, because nobody's retainer automatically covers a return on a transaction that completed last year.
Apply for a Strategic Review
This article is general information only and does not constitute tax advice. Figures and dates are current as at the date of writing; any worked example is illustrative. Always consult a qualified adviser before acting.