14-Day Filing Deadline and Penalties
From 1 March 2019, SDLT returns (SDLT1 + any supplementary forms) must be filed and tax paid within 14 days of the effective date — for most purchases, the date of completion (FA 2003 s.76(1A)). A return must be filed even where no SDLT is due — the filing obligation applies to all notifiable land transactions. Penalties: £100 (up to 3 months late); £200 (over 3 months late); tax-geared 5%/10%/15% of outstanding tax (over 12 months late; careless/deliberate/deliberate with concealment). Late payment interest: Bank of England base rate + 2.5% from the day after the deadline. The £100 fixed penalty applies even if the tax is nil. Reasonable excuse (illness, bereavement, incorrect HMRC guidance) may avoid a filing penalty but does not excuse late payment interest. Always request a copy of the filed SDLT1 from your conveyancer — it is the primary evidence of compliance.
Amendments, Overpayment Relief, and HMRC Enquiries
Amendment window (FA 2003 s.76(3)): amend online within 12 months of the filing deadline — after this, only overpayment relief applies. Overpayment relief (FA 2003 Sch.11A): 4-year window from the effective date to claim overpaid SDLT — the primary route for landlords who missed multiple dwellings relief on past purchases. HMRC enquiry window (FA 2003 Sch.10 para.12): HMRC can open a formal enquiry within 9 months of the filing date (or 9 months from actual filing date if filed late). Common enquiry triggers: multiple dwellings relief claims; mixed-use SDLT rates; unusual transaction structures; linked transactions. Discovery assessments: outside the enquiry window, HMRC can assess additional SDLT within 6 years (careless error) or 20 years (deliberate). On receipt of a Schedule 10 enquiry notice, instruct a specialist tax adviser immediately — HMRC Schedule 36 information notices carry criminal sanctions for non-compliance. Appeals against HMRC determinations go to the First-tier Tax Tribunal within 30 days.