What an SDLT12 or SDLT12A underpaid stamp duty notice means
SDLT12 and SDLT12A notices
HMRC’s manual says its system sends an SDLT12 where it calculates that stamp duty was underpaid. If no payment is recorded, it sends an SDLT12A reminder and may then start debt recovery.
- Check the amount against your SDLT return.
- Check whether payment was already made.
- Keep evidence of the return and payment.
Scroll down for the full analysis.
Read the original guidance here:
What an SDLT12 or SDLT12A underpaid stamp duty notice means
An SDLT12 or SDLT12A means HMRC’s system believes you still owe stamp duty. Check the amount straight away.
HMRC’s manual says an unpaid amount can move to debt recovery if payment is not received and the system continues to show it as outstanding. Act promptly.
What this rule is about
Your SDLT return includes your own stamp duty calculation when you buy property, and HMRC can compare it with information on its system when deciding what it considers payable.
That comparison matters. If the system identifies a shortfall, HMRC’s manual describes an automatic chase process.
This form does not create a new tax bill. It is HMRC requesting an amount that it believes should already have been paid.
What the official source says
HMRC’s internal manual sets out the following sequence. It is guidance on HMRC’s process rather than the law itself.
- If the system finds an underpayment, HMRC issues form SDLT12.
- Form SDLT12 asks for the amount it says is still due.
- A payment slip is included with the form.
- If the system does not record payment within its allowed time after it has issued SDLT12 and requested the amount that it says is still due, it automatically issues form SDLT12A. It does so automatically.
- If payment still does not arrive, HMRC issues form SDLT13.
- Form SDLT13 says debt recovery action will start.
- After that, the system passes the debt details to HMRC’s debt management team.
What this means in practice
Treat the notice cautiously, but do not ignore it. No stated period in the manual tells you how long is allowed before the next form is sent.
Check the notice, your return and your payment records without delay.
- Compare the amount on the notice with the SDLT return.
- Check whether your conveyancer paid the tax for you.
- Find the payment confirmation or bank record.
- Check that HMRC has linked the payment to the correct purchase.
How to analyse it
Start by asking a simple question: has the tax actually been paid? If it has not, determine whether the original return calculation was correct.
A form warns you about HMRC’s view. It does not provide a full explanation of the calculation.
- Read the form number and the amount claimed.
- Identify the property purchase and completion date it relates to.
- Compare HMRC’s figure with the return filed in your name.
- Match any payment to the right SDLT reference.
- Keep copies of the notice, return and payment evidence.
Example
Amira’s SDLT return showed £4,000 of stamp duty. HMRC’s system calculates £4,500 and sends an SDLT12 for £500.
Before paying again, Amira checks her completion papers. Payment records show that £500 was paid.
The reference may not have been matched to the return. What matters is whether HMRC received and recorded that payment, including where a reference may not have been matched to the return, rather than simply the figure on the first notice.
That is the point to resolve.
Why this can be difficult in practice
For many people, SDLT is neither filed nor paid personally. A conveyancer may have done so.
A notice may therefore seem unexpected where a conveyancer handled the filing or payment. This can happen if a payment reference, property address or return details do not match.
Check the links.
- A notice may relate to a payment that has not yet been matched.
- The original SDLT calculation may contain an error.
- The manual gives no public detail on the system’s timing.
- Debt recovery can begin if the amount remains unpaid.
Key takeaways
- An SDLT12 is HMRC’s request for a suspected underpayment.
- An SDLT12A is an automatic reminder under HMRC’s described process.
- Check the return and payment evidence before assuming the amount is right.
Technical analysis
For advisers, and for anyone who wants to check the law behind this page. You do not need this section to understand the guidance above.
Legislation
- FA 2003 section 76 — return includes the buyer’s stamp duty calculation
- FA 2003 section 86 — when stamp duty shown as payable must be paid
- FA 2003 Schedule 12 para 1 — HMRC may demand stamp duty that is due
- FA 2003 Schedule 12 para 5 — recovery of unpaid stamp duty as a crown debt
Official guidance
The pages below are HMRC’s guidance. Guidance is not law. It sets out how HMRC reads the legislation, and it is not binding on you, on a tribunal or on a court. Where guidance and the legislation differ, the legislation wins. HMRC can also change or withdraw guidance, and it may not cover your facts.
Where this is not settled
- The source does not say how a buyer should challenge an amount they think is wrong.
- The source does not confirm whether these form names and automated steps remain HMRC’s current practice.
Evidence you would need
This kind of case is decided on the facts of the individual property. These are the records that usually settle it, and the ones an adviser would ask you for.
- the SDLT return submitted for the purchase
- the SDLT12, SDLT12A or SDLT13 notice received
- proof of any stamp duty payment already made
- the completion statement and documents supporting the tax calculation
Explore this with an AI
Readers often want to test their own situation. Copy the prompt below into ChatGPT, Claude or Gemini. It hands the model the actual legislation for this page rather than letting it answer from memory, and tells it to be explicit about what is uncertain. What comes back is information, not advice – check it against the links above.
I am researching UK Stamp Duty Land Tax (SDLT), which applies in England and Northern Ireland. MY QUESTION What an SDLT12 or SDLT12A underpaid stamp duty notice means [Replace this with your own situation: what you are buying, the price, the dates, who the buyer is, and what you plan to do with the property.] THE LAW THIS TURNS ON - FA 2003 section 76 - return includes the buyer's stamp duty calculation https://www.legislation.gov.uk/ukpga/2003/14/section/76/2025-11-17 - FA 2003 section 86 - when stamp duty shown as payable must be paid https://www.legislation.gov.uk/ukpga/2003/14/section/86/2025-11-17 - FA 2003 Schedule 12 para 1 - HMRC may demand stamp duty that is due https://www.legislation.gov.uk/ukpga/2003/14/schedule/12/paragraph/1/2025-11-17 - FA 2003 Schedule 12 para 5 - recovery of unpaid stamp duty as a crown debt https://www.legislation.gov.uk/ukpga/2003/14/schedule/12/paragraph/5/2025-11-17 Guidance page from HMRC on this topic (guidance, not law): https://www.gov.uk/hmrc-internal-manuals/stamp-duty-land-tax-manual/sdltm60250 HOW I WANT YOU TO ANSWER 1. Work from the legislation above. Read it before answering. Guidance from HMRC is its view of the law, not the law, and does not bind a tribunal or a court. 2. Tell me what the rule actually requires, in plain English. 3. Tell me which facts decide the answer, and which facts would change it. 4. Tell me what evidence I would need to support the position. 5. Be explicit about anything unsettled or fact-sensitive. Do not guess. 6. Your training data has a cutoff and SDLT rates and reliefs change at fiscal events. Say so if you are not sure the law is current. POINTS ALREADY KNOWN TO BE UNCERTAIN ON THIS TOPIC - The source does not say how a buyer should challenge an amount they think is wrong. - The source does not confirm whether these form names and automated steps remain HMRC's current practice. Do not give me a conclusion you cannot support from the provisions above.
Legislation links show Finance Act 2003 as it stood on 2025-11-17. The law may have changed since, and the rules that apply are those in force on the date of your transaction. The official guidance this page is based on is here.
This page was last updated on 1 September 2026
Useful article? You may find it helpful to read the original guidance here: What an SDLT12 or SDLT12A underpaid stamp duty notice means
Search Land Tax Advice with Google
