The Finance Act 2026 introduced a requirement that will affect every conveyancing practice in England and Wales: solicitors who submit Stamp Duty Land Tax returns on behalf of clients must now register with HMRC as tax advisers. The majority of practices have until 18 August 2026 to comply. For firms without an existing HMRC Agent Services Account, the first deadline has already passed.
This is not a minor administrative update. Failure to register means you cannot file SDLT returns, which means your client's Land Registry applications will stall at the point of completion.
What the Finance Act 2026 Requires
Part 7 of the Finance Act 2026 creates a new category of regulated interaction with HMRC. Any professional submitting tax documents, returns or payments on behalf of a client — including SDLT returns, inheritance tax on death, and certain Capital Gains Tax notifications — must hold registration as a tax adviser with HMRC.
For conveyancing solicitors, the principal trigger is SDLT. Every residential purchase, commercial acquisition, and leasehold transaction generates an SDLT return obligation. Under the new regime, the firm submitting that return must be a registered tax adviser.
The Two Deadlines Every Conveyancing Practice Must Know
18 May 2026 — firms without an Agent Services Account. If your practice does not already have an HMRC Agent Services Account, you should have registered by 18 May 2026. This deadline has passed. If you have not yet registered, you are already non-compliant and should act immediately.
18 August 2026 — the general deadline. Firms with an existing Agent Services Account must complete their tax adviser registration by 18 August 2026. Three months may sound like sufficient time. It is not, because HMRC processing times for new registrations can run to four to eight weeks. Applications submitted in late July risk processing delays that put you on the wrong side of the deadline.
What Counts as an Interaction with HMRC
The Finance Act 2026 defines the scope broadly. The following activities bring a solicitor into the registered tax adviser regime:
- Submission of SDLT returns (form SDLT1 and related forms)
- Payment of SDLT on behalf of clients
- Submission of inheritance tax accounts where acting as agent
- Notifications to HMRC of chargeable Capital Gains Tax disposals where acting as agent
- Correction and amendment of previously filed returns in any of these categories
If your firm does any of these regularly — and most conveyancing practices submit SDLT returns as a standard part of every transaction — you are in scope.
Consequences of Missing the Deadline
The practical consequences of missing the August deadline are severe. From 19 August 2026, HMRC systems will reject SDLT submissions from unregistered agents. A rejected SDLT return means:
- The Land Registry will not register the transaction. Land Registry requires evidence that SDLT has been filed and paid as a condition of registration.
- Your client's title remains unregistered. Until registration completes, they are vulnerable to priority disputes and cannot use registered title as security for mortgage purposes.
- You face potential professional negligence exposure. A transaction that cannot complete because your firm failed to maintain regulatory compliance is a significant PI risk.
- Potential SRA referral. Acting in a transaction and being unable to file required tax documents due to an avoidable regulatory failure is a conduct issue.
How to Register as a Tax Adviser
Registration is through your existing Agent Services Account or, if you do not have one, through a new registration process on HMRC's website. You will need:
- Your firm's Unique Taxpayer Reference (UTR) or company registration number
- Details of the individual who will act as the authorised tax adviser for the practice
- Evidence of your professional status — SRA registration number in most cases
- Confirmation of the type of services you provide (select SDLT submissions)
Once registered, you will receive a Tax Adviser Reference Number (TARN). This reference must be quoted on all SDLT submissions from your practice from 19 August 2026.
What This Means for Your Conveyancing Workflow
The registration requirement itself is a one-time administrative step. The operational impact comes from what it enables and what it requires going forward.
Engagement letters must be updated. Your standard engagement letter must now reference your tax adviser registration and include appropriate client authorisation for HMRC interactions. A 64-8 agent authorisation in digital form provides the cleanest basis for this.
Client AML obligations intensify. The Finance Act 2026 registration regime sits alongside existing MLR 2017 obligations. As a registered tax adviser, your AML screening obligations extend to every client for whom you submit SDLT. This is not new — it was always required under MLR 2017 — but the new registration regime makes non-compliance more visible to your supervisor.
Audit trails matter more. HMRC may audit registered tax advisers. Your records of client authority, submission dates, and SDLT calculations must be complete and retrievable on demand.
How SignFlow Helps
SignFlow Now is built specifically for the post-Finance Act 2026 conveyancing workflow. The platform integrates:
HMRC Agent Authorisation (64-8): Digital 64-8 forms sent to clients via a compliant signing workflow, with a Certificate of Completion for each authorisation. Clients sign in minutes on any device.
SDLT Workflow: Integrated SDLT preparation and submission tracking, with audit records aligned to the new tax adviser registration requirements.
AML Declarations and Identity Verification: Biometric identity checks, sanctions screening, and PEP checks built into your client onboarding flow — meeting the combined SDLT and MLR 2017 obligations in one workflow.
Engagement Letters with Compliant Wording: Updated engagement letter templates that include the new tax adviser reference requirements and client consent language.
Every document is stored with a SHA-256 cryptographic audit trail. If HMRC audits your practice, you have complete, timestamped records of every client authorisation and every interaction.
Action Plan for Conveyancing Practices
The 18 August 2026 deadline is approaching. Here is what to do this week:
- Check whether your firm has an Agent Services Account — if not, register immediately
- Begin the tax adviser registration process — allow eight weeks for processing
- Identify all active conveyancing matters and confirm SDLT submission obligations
- Update your engagement letter template to include tax adviser reference language
- Brief your conveyancing team on the new workflow requirements
- Review your AML procedures for SDLT-related clients
Practices that act now will complete registration with time to spare. Practices that wait until August risk missing the deadline and being unable to complete transactions.