Compliance
Compliance Overhaul: What UK Businesses Should Know About the Modernised Tax-Adviser Registration and Marketplace VAT Rules
New rules for tax adviser registration and expanded VAT liability for online marketplaces are transforming UK tax compliance—businesses and agents need to prepare now.
By NomadicTax Research Team • 5-8 min read • July 1, 2026
## Overview of Key Regulatory Changes
Two major compliance-facing reforms have been announced in the Tax Update 2026 package:
| Reform | Purpose | Effective As... |
|---|---|---|
| **Modernising and Mandating Tax Adviser Registration (MMTAR)**: all paid tax advisers interacting with HMRC must register via the Agent Services Account. | To raise standards, reduce the tax gap and ensure consistency in who can provide tax-advice services. | *Rollout begins 18 May 2026*, continues in phases until 31 March 2027. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
| **Online Marketplace VAT liability extension** | To ensure online sellers—especially overseas or remote ones—comply with UK VAT rules and remove unfair competition benefiting non-compliant vendors. | Proposed via consultation as part of the June 2026 policy suite. ([gov.uk](https://www.gov.uk/government/publications/summary-of-tax-update-2026-simplification-modernisation-and-fairness/tax-update-2026-simplification-modernisation-and-fairness-summary?utm_source=openai))
## What Businesses and Agents Must Do Now
- Tax advisers (agents) must check whether they are within the scope of compulsory registration. Use HMRC’s interactive checker tool. Apply for an ASA if required. ([gov.uk](https://www.gov.uk/government/news/tax-advisers-check-if-you-need-to-register-under-new-rules?utm_source=openai))
- Online sellers via marketplaces need to monitor how liability rules may change. Collect evidence of VAT registration status, marketplace terms, and customer contracts; prepare to adjust pricing and processes to account for VAT collection obligations.
## Detailed Benefits and Risks
**Benefits**
- Trust and consistency: clients will have greater confidence that advisers meet minimum standards. Less risk of dealing with unregistered or low-quality advice.
- Environment ripe for clean compliance: online sellers who have been compliant will be less disadvantaged compared to those avoiding VAT.
- Better digital infrastructure: the reforms signal further digitisation (e.g. Option to Tax via digital channels). Many stakeholders will benefit by being early adopters. ([gov.uk](https://www.gov.uk/government/publications/summary-of-tax-update-2026-simplification-modernisation-and-fairness/tax-update-2026-simplification-modernisation-and-fairness-summary?utm_source=openai))
**Risks / Challenges**
- Costs of compliance: searchable documents, systems, pricing adjustments, registering with HMRC, training staff.
- Uncertainty while consultations are ongoing: some rules are not final; e.g. marketplace liability is still under review.
- Penalties may increase or become stricter under new rules, particularly for reckless untrue statements. ([gov.uk](https://www.gov.uk/government/publications/summary-of-tax-update-2026-simplification-modernisation-and-fairness/tax-update-2026-simplification-modernisation-and-fairness-summary?utm_source=openai))
## Example Case
- A business runs an online marketplace platform connecting artisans with UK customers. Under the new proposed VAT online marketplace liability extension, if some artisans are not VAT-registered or under declare VAT, the platform may become responsible for ensuring VAT compliance. Failing that, the platform may be liable.
- A sole practitioner tax adviser who has been giving advice informally without an Agent Services Account (ASA) receives HMRC correspondence: they must register and comply with the new rules, or risk not being legally recognised to act on clients’ behalf.
## Action Plan Checklist
1. **For agents / advisers**: review your circumstances vs HMRC’s guidance. Register when your tranche opens; ensure you have ASA where needed.
2. **For marketplace operators**: audit existing terms of business; ensure you have VAT-registered users; possibly revise contracts or collect identities following marketplace liability rules.
3. **For all businesses**: follow consultations, submit feedback. Plan systems updates early—digitisation, reporting, VAT workflows. Stay tuned to Finance Bill 2026-27 when final legislative language emerges.
## Bottom Line
Compliance is becoming more rigorous in the UK. Between adviser registration, marketplace VAT liability, and digitisation efforts, businesses and professionals need to assess exposure now. Taking steps today reduces risk tomorrow—mitigate surprises, avoid penalties, and build stronger compliance foundations.