Stamp Duty Land Tax: Definitions and Chargeable Events Explained

SDLT meaning of contract, completion and conveyance

For SDLT rules on contracts and substantial performance, the terms “contract”, “completion” and “conveyance” are defined very widely. This matters because SDLT can arise before formal completion, so you must identify whether there is an agreement, whether the later deal is the completion of that same transaction, and what legal instrument gives effect to it.

• A “contract” means any agreement, not just a formal signed conveyancing contract.
• “Completion” means the later completion of the land transaction originally proposed, between the same parties, and broadly in line with the contract.
• A “conveyance” includes any written or electronic instrument, and specifically includes a lease.
• The idea of “substantial conformity” means the final transaction does not need to match every detail exactly, but it must still broadly reflect the original agreement.
• Practical difficulties often arise where arrangements are informal, changed over time, or involve different parties, assignments, nominees or significantly altered terms.

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SDLT contracts and substantial performance: what “contract”, “completion” and “conveyance” mean

This page explains three short but important definitions used in the SDLT rules on contracts and substantial performance. They matter because SDLT can sometimes be triggered before formal completion, and these definitions help determine when the tax rules apply and what counts as the later completion of the deal.

What this rule is about

Under the SDLT rules, a land transaction is often taxed on completion. But where a contract is substantially performed before formal completion, SDLT may be brought into charge earlier. To apply those rules, you need to know what counts as a contract, what counts as completion, and what is meant by a conveyance.

The source material gives broad definitions. Those broad definitions matter because they stop the rules being limited only to formal written contracts or traditional paper transfer documents.

What the official source says

The official source states that:

• “Contract” means any agreement.
• “Completion” means completion of the land transaction proposed, between the same parties, in substantial conformity with the contract.
• “Conveyance” includes any instrument, whether in written or electronic form, including a lease.

These definitions appear in the SDLT legislation dealing with contracts and substantial performance.

What this means in practice

The definition of contract is deliberately wide. It is not limited to a formal signed sale contract in the usual conveyancing sense. If there is an agreement for a land transaction, that may be enough for these rules to engage.

The definition of completion is also important. It does not simply mean any later transfer of land. It means the eventual completion of the land transaction that the contract contemplated, involving the same parties, and carried out in substantial conformity with that contract. In other words, the later completion must broadly match the earlier agreement.

This matters because the SDLT rules on substantial performance are designed to connect an earlier contract with the later legal completion of the same deal. If the eventual transaction is materially different, or not between the same parties, there may be questions about whether it is truly the completion of that original contract for these purposes.

The definition of conveyance is also broad. It includes any instrument in written or electronic form, and specifically includes a lease. So the rules are not confined to a traditional transfer deed. They can apply to the various legal instruments used to give effect to a land transaction.

How to analyse it

When looking at a transaction under these rules, it helps to ask the following questions:

• Is there an agreement at all? If so, it may count as a contract for SDLT purposes, even if it is informal or not in the usual form.
• What land transaction does that agreement propose?
• Has the transaction been substantially performed before formal completion? That question is governed by the wider substantial performance rules, but these definitions help identify the relevant contract and later completion.
• When the deal is later completed, is it between the same parties?
• Is the completed transaction in substantial conformity with the earlier contract? If the final deal differs significantly, the position may be less straightforward.
• What instrument gives effect to the transaction? A transfer, lease, or electronic instrument may all fall within the concept of a conveyance.

The phrase “substantial conformity” is especially important. It suggests that exact identity is not required in every detail, but the final completed transaction must still broadly correspond to what the contract provided for.

Example

Suppose a buyer and seller agree that the buyer will acquire a commercial property. The buyer is allowed into possession before the transfer is formally completed. That early possession may raise the issue of substantial performance under the wider SDLT rules.

If the parties later complete the transfer in line with that agreement, that later step is likely to be the “completion” of the land transaction proposed by the contract, provided it is between the same parties and is in substantial conformity with what was originally agreed.

But if the final arrangement is materially recast, for example because a different party acquires different property on significantly different terms, it may be harder to say that the later transaction is the completion of the original contract in the statutory sense.

Why this can be difficult in practice

The statutory definitions are short, but applying them can be fact-sensitive.

First, because “contract” means any agreement, the real issue may be identifying whether there was in fact an agreement and what its terms were. That may be straightforward in a standard conveyancing transaction, but less so where arrangements were informal, conditional, or varied over time.

Second, “substantial conformity” is not the same as exact conformity. That leaves room for judgement. Minor changes may not prevent the later transaction from being the completion of the earlier contract, but more significant changes may do so.

Third, the requirement that completion be between the same parties can create difficulty where rights are assigned, nominees are introduced, or the transaction structure changes before completion. The source material does not resolve those wider issues by itself, so the answer depends on the broader SDLT rules and the facts.

Key takeaways

• For these SDLT rules, a contract means any agreement, not just a formal written contract.
• Completion means the later completion of the same land transaction, between the same parties, and broadly in line with the contract.
• Conveyance is a wide term and includes written or electronic instruments, including a lease.

This page was last updated on 24 March 2026

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