How long HMRC has to enquire into an SDLT return

Q: What mistakes do buyers and conveyancers make?

Counting from completion. The nine months run from the filing date, or from delivery or amendment, not from the effective date. Assuming an amendment is risk free. A refund amendment gives HMRC a fresh window to enquire into the amendment. Relying on the window closing. Discovery remains available for years if information was not made available or conduct fell short. Applying SDLT rules elsewhere. Purchases in Scotland and Wales fall under Land and Buildings Transaction Tax and Land Transaction Tax, which have their own rules; see SDLT, LBTT and LTT compared. If HMRC opens a check into your return, tax investigation insurance pays your accountant's fees. Solar Protect cover pays up to £100,000 with no excess; it never pays tax, interest or penalties. Read how our cover works or get a quote.

HMRC can open an enquiry into an SDLT return by written notice within nine months after the filing date, which is the last day of the 14 day period after the effective date. If the return is filed late, the nine months run from the day it is delivered, and if the buyer amends it, a new nine month window opens from the amendment. After that, HMRC can only reopen the transaction by a discovery assessment, normally within 4 years of the effective date, or 6 or 20 years where the loss of tax was careless or deliberate.

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When does the nine month window start and end?

The rules are in Part 3 of Schedule 10 to the Finance Act 2003. Paragraph 12 lets HMRC enquire into a return if it gives notice to the purchaser before the end of the enquiry period, and paragraph 12(2)(a) sets that period as nine months after the filing date where the return was delivered on or before that date. Section 76(1) requires the return to be delivered before the end of 14 days after the effective date, and paragraph 2 of Schedule 10 defines the filing date as the last day of that period. HMRC’s Stamp Duty Land Tax Manual at SDLTM80010 adds that an enquiry may be opened without giving a reason and by written notice to the purchaser.

Illustration only. A purchase completes on 3 March 2026. The filing date is 17 March 2026. If the return is filed on time, HMRC can give notice of enquiry until 17 December 2026.

The window runs from the filing date, not the date the return was actually sent. Filing early does not shorten it. The return deadline itself is covered in SDLT return deadline and penalties.

What if the return was filed late?

Paragraph 12(2)(b) says that where the return is delivered after the filing date, the enquiry period is nine months after the date on which it was delivered. A late return therefore stays open longer, as well as attracting penalties.

Illustration only. For the same purchase, a return delivered on 30 April 2026 can be the subject of an enquiry notice until 30 January 2027.

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Does amending the return reopen the window?

Yes, for the amendment. Paragraph 6(3) allows the buyer to amend the return up to 12 months after the filing date, and paragraph 12(2)(c) gives HMRC nine months after the date the amendment was made to enquire. Paragraph 12(3) says a return can only be the subject of one notice of enquiry, except one given because of an amendment. If that notice is given after the original window has closed, or after an earlier enquiry has been completed, paragraph 13(2) limits the enquiry to what the amendment relates to or affects.

Illustration only. The buyer who filed on time amends the return on 1 February 2027 to claim a refund. HMRC can enquire until 1 November 2027, but only into the amendment and what it affects. The process is explained in how to amend an SDLT return.

A separate correction power should not be confused with an enquiry. Under paragraph 7, HMRC may correct obvious errors or omissions in a return by notice, but not more than nine months after the return was delivered, or after an amendment that made the correction necessary. The buyer can reject the correction.

What about further returns for contingent or linked transactions?

Some transactions need a further return, for example when contingent consideration becomes certain under section 80, when a relief is withdrawn under section 81, or when a later linked transaction occurs under section 81A. Paragraph 12(2A) says that if HMRC opens an enquiry into such a further return within its own window, and it appears necessary to enquire into an earlier return as well, it may do so even though the earlier window has passed. See SDLT on overage and contingent consideration.

What does an enquiry cover and how does it end?

Under paragraph 13(1), an enquiry extends to anything in the return, or required to be in it, that relates to whether tax is chargeable or the amount. If HMRC believes during an enquiry that the self assessment is too low and there is likely to be a loss of tax unless it acts at once, paragraph 17 allows it to amend the self assessment immediately.

The enquiry ends when HMRC issues a closure notice under paragraph 23, stating either that no amendment is needed or making the amendments required. A buyer who thinks an enquiry is dragging on can apply to the tribunal under paragraph 24 for a direction that HMRC issues a closure notice within a specified period, and the tribunal must give the direction unless satisfied HMRC has reasonable grounds for not doing so. See HMRC closure notices.

Records should be kept with this in mind. Paragraph 9 requires the buyer to preserve records, including the contract, the transfer and records of payments, until the later of the sixth anniversary of the effective date and the end of any enquiry or of HMRC’s power to enquire. Paragraph 11 sets a penalty of up to £3,000 for failing to do so.

When can HMRC use a discovery assessment instead?

Once the window has closed without an enquiry, or an enquiry has been completed, HMRC needs a discovery assessment under paragraph 28 to collect more tax. Where a return was delivered, paragraph 30 allows this in only two cases:

the loss of tax is attributable to fraudulent or negligent conduct by the buyer, a person acting for the buyer, or a partner of the buyer; or
when HMRC ceased to be entitled to open an enquiry, or completed its enquiry, it could not reasonably have been expected to be aware of the problem on the basis of the information made available to it.

Paragraph 30(4) treats information as made available if it is in the return, in documents or information produced for an enquiry, or could reasonably be inferred from those, or was notified to HMRC in writing by or for the buyer. Paragraph 30(5) prevents an assessment where the return followed the practice generally prevailing at the time. A short covering letter sent with the return explaining a relief or valuation can therefore protect the buyer later. The general rules are covered in discovery assessments.

How long does HMRC have for a discovery assessment?

Paragraph 31 sets the limits, all measured from the effective date of the transaction rather than from the return:

Situation	Time limit
General rule	4 years after the effective date
Loss of tax brought about carelessly by the buyer or a related person	6 years after the effective date
Loss brought about deliberately, or linked to certain failures such as not delivering a return or not complying with avoidance scheme disclosure rules	20 years after the effective date

Where the buyer has died, paragraph 31(4) requires any assessment on the personal representatives to be made within 4 years after the death. An objection that an assessment is out of time can only be made on appeal against it. For how these limits compare with other taxes, see how far back HMRC can go.

What mistakes do buyers and conveyancers make?

Counting from completion. The nine months run from the filing date, or from delivery or amendment, not from the effective date.
Assuming an amendment is risk free. A refund amendment gives HMRC a fresh window to enquire into the amendment.
Relying on the window closing. Discovery remains available for years if information was not made available or conduct fell short.
Applying SDLT rules elsewhere. Purchases in Scotland and Wales fall under Land and Buildings Transaction Tax and Land Transaction Tax, which have their own rules; see SDLT, LBTT and LTT compared.

If HMRC opens a check into your return, tax investigation insurance pays your accountant’s fees. Solar Protect cover pays up to £100,000 with no excess; it never pays tax, interest or penalties. Read how our cover works or get a quote.

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Reviewed by Christine Anderson, Broker, Solar Protect. Last reviewed 24 October 2026. Part of Accountapedia, the Solar Protect guide to UK tax and accounting. This page is general information, not personalised advice.