Understanding SDLT Charges: Contract Substantial Performance Before Formal Completion

When SDLT can arise before completion

SDLT usually becomes due when a property transaction completes, but it can arise earlier if the contract has been substantially performed before formal completion. This depends on the facts, especially whether the buyer has already taken enough benefit of the property or the deal in practice.

• In most property transactions, the SDLT charge point is completion.
• If the buyer takes possession, starts using the property, or otherwise receives significant benefit under the contract before completion, SDLT may arise earlier.
• Whether a contract has been substantially performed is a factual question, so the real position matters more than labels or wording alone.
• This is mainly a timing rule: it affects when SDLT is triggered, not whether the transaction is within SDLT at all.
• Early substantial performance can affect SDLT filing, payment, and how advisers monitor the transaction.
• Care is needed where buyers are given early access, occupation, or rights before completion, as a deal can still be pre-completion in conveyancing terms but already chargeable for SDLT.

Scroll down for the full analysis.

When SDLT can arise before completion: contracts that are substantially performed

This page explains an important SDLT timing rule. In most property transactions, SDLT is triggered when the deal completes. But if the buyer takes enough of the benefit of the contract before formal completion, SDLT can arise earlier. The key question is whether the contract has been “substantially performed”, and that is a factual question.

What this rule is about

SDLT normally applies to a land transaction when the transaction is completed. Completion is usually the point at which the transfer is formally carried out.

However, the legislation also looks at what has happened in practice before completion. If a contract for a land transaction is substantially performed before formal completion, SDLT can be charged at that earlier stage instead of waiting for completion.

This matters because parties sometimes exchange contracts and then allow the buyer to take possession, start using the property, or otherwise enjoy the benefit of the deal before the legal transfer is completed. The SDLT rules do not always wait for the final paperwork if the transaction has already moved far enough in substance.

What the official source says

The HMRC manual states two core points.

First, in the great majority of cases SDLT arises on completion.

Second, SDLT will arise earlier if a contract governing the land transaction is substantially performed before formal completion.

The manual also makes clear that substantial performance is a question of fact. That means there is no single label or form of wording that decides the issue on its own. What matters is what has actually happened under the contract.

The source points to further HMRC guidance on when substantial performance takes place. The page here does not set out a full test. Its main purpose is to establish that early SDLT charges can arise where the contract has effectively been acted on before completion.

What this means in practice

You should not assume that SDLT only becomes relevant on the day of completion. If the buyer has already moved into the property, started to enjoy it, or otherwise acted under the contract in a way that amounts to substantial performance, the SDLT charge may already have arisen.

That can affect timing, filing, and payment. It can also affect how a transaction is recorded and monitored by conveyancers and advisers. A transaction that appears “not yet completed” in conveyancing terms may still have reached the SDLT charge point.

The practical message is simple: look at the facts on the ground, not just the formal completion date.

How to analyse it

When considering whether SDLT has arisen before completion, it helps to ask the following questions:

• Is there a contract governing a land transaction?
• Has formal completion taken place yet?
• If not, has the contract nevertheless been substantially performed?
• What has the buyer actually been allowed to do under the contract?
• Do the facts show that the buyer has already received a significant part of the benefit of the transaction before completion?

Because substantial performance is a question of fact, the analysis depends on the real substance of the arrangement. Labels used by the parties may be relevant, but they are not the whole answer. The legal and practical position must be looked at together.

In wider SDLT analysis, this is mainly a timing rule. It does not change the basic point that the transaction must be one within the scope of SDLT. Instead, it determines whether the tax charge arises on completion or at an earlier stage because the contract has already been substantially performed.

Example

Illustration: a buyer exchanges contracts to acquire commercial land, but completion is scheduled for a later date. Before that date, the buyer is allowed into occupation under the contract and begins using the land for its business. Even though legal completion has not yet happened, the facts may show that the contract has been substantially performed. If so, SDLT may arise at that earlier point rather than on the later completion date.

The outcome depends on the actual facts and the legal effect of what the parties have done.

Why this can be difficult in practice

The source material expressly says that substantial performance is a question of fact. That is often where the difficulty lies. Transactions do not always follow a neat sequence. Parties may allow early access for limited purposes, permit works before completion, or make interim arrangements that are not easy to classify.

The hard question is often whether what has happened is merely preparatory, or whether it is enough to show that the contract has already been substantially carried into effect. The answer may depend on the precise contractual rights given, what happened in reality, and when it happened.

This is also an area where conveyancing language and tax analysis can diverge. A transaction may still be “pre-completion” in ordinary property terms, but that does not settle the SDLT position.

Key takeaways

• In most cases, SDLT arises on completion.
• If a contract is substantially performed before completion, SDLT can arise earlier.
• Whether there has been substantial performance depends on the facts, not just the formal stage of the transaction.

This page was last updated on 24 March 2026

Useful article? You may find it helpful to read the original guidance here: Understanding SDLT Charges: Contract Substantial Performance Before Formal Completion

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