Tax disputes resolution

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Tax disputes resolution

HMRC now has access to more information than ever before and with increasing pressure on public finances, it is expected to use the full extent of its powers to open tax investigations, driven by a clear focus on reducing the tax gap.

HMRC investigations vary in scope and severity, from routine compliance checks and information requests to more serious enquiries such as Code of Practice 9 cases, R&D reviews and discovery assessments, each requiring a tailored and informed response.

At Forvis Mazars, we support both individuals and businesses, including sole traders, limited companies, trusts, partnerships and high net‑worth individuals.

How our Tax Disputes Resolution specialists can support you

With experienced professional representation, we can take control of the process, managing HMRC investigation, protecting your position, and ensuring fair and proportionate treatment at each stage.

Our nationwide team includes ex-senior HMRC investigators and experienced tax dispute specialists with deep, practical insights across multiple HMRC departments. We guide you through each phase of the enquiry, clearly explaining your options, anticipating HMRC’s lines of questioning, and identifying the specific risks HMRC is seeking to examine. This informed, proactive approach helps progress enquiries efficiently towards resolution.

Where historic errors or undeclared income need to be addressed, we can guide you through HMRC’s voluntary disclosure facilities, helping identify the most appropriate route and negotiating reduced penalties wherever possible.

If you have received a letter from HMRC or are worried that you may need to disclose a historic inaccuracy, get in touch on -

Our Tax dispute resolution services include

  • Code of Practice 9
  • Code of Practice 8
  • R&D enquiries
  • Disclosures (Worldwide Disclosure Facility/Digital Disclosure Service/Let Property Campaign etc)
  • Appeals against HMRC decisions
  • Behavioural penalty representations and penalty suspension applications
  • Schedule 36 - reviewing HMRC information requests
  • Nudge letters – advice on approach; review tax positions and disclosure process
  • Individual ‘S9a’ and company ‘Para 24’ enquiries and ‘compliance checks’
  • Offshore matters (Including transfer of assets abroad)
  • Litigation services (including Alternative Dispute Resolution with HMRC)
  • Settlement of mass marketed avoidance schemes
 

 

Speak to a member of our tax disputes team

Get in touch

 

Tax disputes FAQs

What is an HMRC dispute?

An HMRC dispute arises when HMRC investigate the accuracy of a tax return, position taken, or historic tax treatment. An HMRC investigation can range from routine enquiries to formal investigations and disputes over penalties, interest or alleged underpayments.

What can trigger a tax dispute or HMRC tax investigation?

An HMRC investigation can be triggered because of inaccuracies in tax returns, information received from third parties, sector‑wide reviews, or random selection. A tax dispute does not necessarily mean wrongdoing, but it does require careful management.

What types of HMRC enquiries or tax investigations are there?

These can include informal reviews, compliance checks, aspect enquiries, full enquiries, Code of Practice 8 (COP8) or Code of Practice 9 (COP9) investigations, as well as disputes over penalties or assessments.

When should you seek professional help for a tax dispute?

You should consider obtaining specialist professional support in the following circumstances:

  • You believe you have made historic errors when submitting UK tax returns or failed to declare any income or gains
  • You have received a letter, notice or assessment you don’t understand
  • HMRC has opened an enquiry or tax investigation into you, or your business’s historic tax affairs
  • You believe a tax decision is incorrect
  • You wish to challenge penalties or negotiate a settlement

Can you instruct an adviser if you’ve already responded to HMRC?

Many people engage with a professional after attempting to handle matters by themselves. We can step in at any stage to review your position and help strengthen your case. We also work closely alongside existing advisors (both lawyers and accountants) to help them resolve their clients' historic tax affairs.

Can an adviser communicate with HMRC on my behalf?

With your authorisation, we can act as your representative, handling all correspondence, attending meetings and negotiating directly with HMRC on your behalf.

An image of an office building with a blue sky background
22 Apr 2026

What is Alternative Dispute Resolution?

Alternative Dispute Resolution is a formal mediation process that can be used to unlock long-running tax disputes with HMRC. Alternative Dispute Resolution can be an effective way of reaching a mutually acceptable settlement, whilst avoiding potentially costly and time-consuming litigation.

Read more
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22 Apr 2026

What is a Cross-Tax enquiry?

A cross tax or full enquiry is an all-encompassing review of a business’s historic corporation tax, VAT and employer duties (PAYE/NIC) position, seeking to understand if respective tax returns, including any claims, have been filed correctly. This contrasts with an aspect enquiry, where HMRC are looking to check a specific entry or matter associated within a tax return.

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22 Apr 2026

What to do if you receive a letter from HMRC

If you receive a letter from HMRC suggesting your historic tax affairs may be incorrect, this can be very unnerving. Whether your letter relates to a compliance check or another tax matter, knowing what to do next and having the right specialist support can save you time, stress, and in some cases, money.

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22 Apr 2026

Understanding HMRC Code of Practice 9 (COP9)

HMRC’s Code of Practice 9 (COP9) is one of the most serious civil tax investigation procedures used by the UK tax authority. COP9 cases require careful handling, strategic disclosure and specialist representation due to the significant financial, legal and reputational risks.

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