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Stamp Duty (SDLT): is it based on exchange or completion date? (UK)

For SDLT (England & NI), HMRC uses the “effective date”. It’s usually completion, but can be earlier if the contract is substantially performed. Quick example inside.

Published: 19/05/2026 • Last verified: 19/05/2026

The short answer

For SDLT (Stamp Duty Land Tax) in England and Northern Ireland, HMRC uses the “effective date” of the transaction. In a straightforward house purchase, that’s usually the completion date — not the exchange date.

However, HMRC guidance also explains that a contract can become effective earlier than completion if it is “substantially performed” (for example, if the buyer takes possession, or pays most of the price). For anything unusual, your conveyancer will confirm what applies.

A tiny example

You exchange on 01/05/2026 and complete on 30/05/2026.

  • In the common case, SDLT is treated as based on the effective date at completion (30/05/2026).
  • If the contract had been substantially performed before completion (an exception HMRC describes), the effective date could be earlier than 30/05/2026.

This is why you’ll often see “completion date” used in everyday SDLT discussions — but HMRC’s rule is the effective date, which can sometimes differ.

FAQ
Is this the same in Wales or Scotland?
No. Wales uses Land Transaction Tax (LTT) and Scotland uses LBTT. This post is about SDLT (England and Northern Ireland).
What does HMRC mean by ‘substantial performance’?
HMRC guidance describes situations where a contract is treated as effective earlier than completion, such as taking possession or paying a substantial amount of the price. The exact definitions are in HMRC’s SDLT manual.
Sources