Introduction
Filing an SDLT return late is one of the most common compliance failures in conveyancing. The 14-day deadline from the effective date of the transaction is tight, and when completions cluster at month-end or over holiday periods, it is easy for returns to slip past the deadline.
This guide explains the penalty regime in full — what you will be charged, how interest works, what constitutes a reasonable excuse, and how to appeal using the SDLT46 form.
The 14-Day Filing Deadline
The SDLT return (SDLT1) must be filed with HMRC within 14 days of the effective date of the transaction. The effective date is usually the completion date, but it can be earlier if the purchaser takes possession or substantially all of the consideration is paid before completion.
The deadline is 14 calendar days, not working days. If the 14th day falls on a weekend or bank holiday, the deadline does not extend to the next working day.
When Does the Clock Start?
| Scenario | Effective Date |
|---|---|
| Standard completion | Date of completion |
| Purchaser moves in before completion | Date of entry into possession |
| Substantially all consideration paid before completion | Date of payment |
| Contract substantially performed | Date of substantial performance |
Penalty Structure
HMRC imposes automatic penalties for late filing. These are separate from any penalties for late payment of the tax itself.
Fixed Penalties
| Delay | Penalty |
|---|---|
| 1 day to 3 months late | £100 |
| Over 3 months late | £200 |
These fixed penalties apply regardless of the amount of tax due. Even if the SDLT liability is nil, the penalty still applies if the return is filed late.
Tax-Related Penalties (Returns Over 12 Months Late)
For returns filed more than 12 months after the effective date, HMRC can impose additional tax-related penalties:
| Behaviour | Penalty (% of tax due) |
|---|---|
| Reasonable care taken | 0% |
| Careless | Up to 30% |
| Deliberate | Up to 70% |
| Deliberate and concealed | Up to 100% |
These are in addition to the fixed penalties above.
Daily Penalties
HMRC also has the power to impose daily penalties of up to £60 per day for returns that remain outstanding after a penalty notice has been issued. In practice, daily penalties are relatively rare for SDLT returns but remain a possibility for persistent non-compliance.
Interest on Late Payment
Separate from filing penalties, HMRC charges interest on any SDLT that is paid late. Interest runs from:
- 30 days after the penalty notice (for penalty amounts)
- The filing deadline (for the SDLT itself)
Interest is charged at the HMRC late payment rate, which is currently Bank of England base rate plus 2.5%.
Interest accrues daily and is not capped. On large transactions, this can become significant quickly.
Reasonable Excuses
HMRC may cancel a penalty if the taxpayer had a reasonable excuse for filing late. A reasonable excuse is something that prevented the return from being filed on time and was beyond the taxpayer's control.
What HMRC Accepts
- Serious illness or bereavement of the person responsible for filing
- Postal delays or loss (where the return was sent in time)
- HMRC system failures that prevented electronic filing
- Unforeseen events such as fire, flood, or theft of records
- Death of the purchaser before the deadline
What HMRC Does Not Accept
- Pressure of work or being busy
- Ignorance of the filing deadline
- Reliance on a third party (such as a solicitor) who failed to file — the obligation rests with the purchaser, not the agent
- IT problems at the firm (unless HMRC's own system was unavailable)
- Difficulty obtaining information for the return
The "Reasonable Excuse" Test
The excuse must have existed for the entire period of default, and the return must have been filed without unreasonable delay once the excuse ceased to apply.
For example, if a solicitor was hospitalised for two weeks after completion, that covers the initial 14-day period. But if they then waited a further month after being discharged before filing, the excuse may not cover the full period.
How to Appeal: The SDLT46 Form
Appeals against SDLT penalties are made using the SDLT46 form — "Notice of Appeal Against a Penalty." This is a paper-only form that must be posted to HMRC.
Time Limit
The appeal must be made within 30 days of the date of the penalty notice. Appeals submitted after 30 days may still be accepted at HMRC's discretion if there is a reasonable excuse for the late appeal.
What the Form Requires
The SDLT46 asks for:
- Purchaser details — name and address (matching the SDLT1)
- Property details — address, postcode, house number
- UTRN — the Unique Transaction Reference Number from the SDLT5 certificate
- Agent details — if the return was filed by a solicitor
- Penalty details — date of the determination notice and amount
- Whether to postpone payment — you can request HMRC not to demand payment while the appeal is pending
- Grounds of appeal — either:
- The return was not delivered late (provide the effective date and date sent), or
- A reasonable excuse (provide full details)
Where to Send It
HM Revenue and Customs BT — Stamp Duty Land Tax BX9 1HD United Kingdom
What Happens After You Appeal
- HMRC considers the appeal
- If accepted: the penalty is cancelled and you are notified in writing
- If rejected: HMRC writes to explain the decision, and you can either:
- Request a review by a different HMRC officer
- Appeal to the First-tier Tribunal (Tax Chamber)
StampSorted can generate a pre-filled SDLT46 form from your transaction data — saving time and ensuring accuracy. Get early access.
Practical Tips for Avoiding Late Filing
1. File on the Day of Completion
Do not wait. The 14-day deadline is shorter than most conveyancers think, especially over holiday periods. Best practice is to file the return on the same day as completion.
2. Automate Your Deadline Tracking
Use software that automatically calculates and flags the 14-day deadline. Manual diary entries are error-prone.
3. Prepare the Return Before Completion
Pre-populate the SDLT return with all available information before the completion date. On the day, you only need to confirm the effective date and consideration, then submit.
4. Have a Backup Process
If your primary filing software fails, have a backup method ready. HMRC's own online service can be used in emergencies.
5. Document Everything
If you do file late, document why immediately. A contemporaneous file note is far more persuasive than a reconstructed explanation months later when HMRC asks.
6. Pay the Tax Separately If Needed
You can pay the SDLT before or at the same time as filing the return. Do not delay filing because the payment is not ready — file the return on time and arrange payment separately.
Multiple Penalties on the Same Transaction
It is possible to receive multiple penalties on a single transaction:
- A fixed penalty for late filing (£100 or £200)
- A penalty for late payment of the tax
- Interest on both the unpaid tax and the unpaid penalties
- Tax-related penalties if over 12 months late
These can add up quickly. On a £500,000 purchase with £12,500 SDLT due, a 6-month delay could result in:
- £200 fixed penalty
- ~£400 in interest on unpaid SDLT
- Interest on the penalty itself
- Total exposure: ~£650+ before any tax-related penalties
Key Takeaways
- 14 calendar days — not working days, no extensions for weekends
- £100 fixed penalty even on nil returns — there is no de minimis
- Reasonable excuse is narrowly defined — "busy" is not an excuse
- Appeal within 30 days using SDLT46 — don't miss this deadline too
- File on completion day — the single best way to avoid penalties
Related Guides
- SDLT Rates 2026: Complete Guide — all current rates and thresholds
- Tax Adviser Registration 2026 — the HMRC registration deadline your firm can't miss
- SDLT Reliefs and Exemptions — reliefs that could reduce the liability you're filing
Calculate your SDLT liability instantly with our free SDLT Calculator.
Check your firm's readiness for the May 2026 tax adviser registration deadline with our Compliance Checker.