How to Dispute a Property Tax Assessment

Property transactions in the UK carry significant tax consequences, and HMRC has substantial powers to issue assessments, raise queries, and challenge the figures on your return. If you've received a property tax assessment you believe is incorrect, whether for capital gains tax, stamp duty land tax, or income tax on property profits, you have the right to dispute it.

This guide explains the types of property tax assessments most commonly challenged, the grounds on which they can be disputed, and the step-by-step process for taking your challenge forward.

What Is a Property Tax Assessment?

A property tax assessment is a formal determination by HMRC of how much tax you owe in connection with a property transaction or rental income. It arises when HMRC believes the amount of tax you've declared, or paid, is less than it should be, or when it calculates a different figure from the one you submitted.

The most common types of property tax assessments subject to dispute include:

• Capital Gains Tax (CGT) assessments – issued when HMRC disputes the gain you've calculated on the disposal of a property, for example, disagreeing with the valuation used, the costs deducted, or the reliefs claimed.
• Stamp Duty Land Tax (SDLT) assessments – raised when HMRC believes you've applied the wrong rate, failed to report a transaction correctly, or incorrectly claimed a relief.
• Income tax assessments on rental income – arising from enquiries into letting income, disputed expenses, or disagreements about how rental profits have been calculated.
• Corporation tax assessments on property profits – for companies involved in property development or investment where HMRC challenges the tax treatment of transactions.

In some cases, disputes arise not because an assessment has been raised, but because you believe you've overpaid tax on a property transaction and want to reclaim it. SDLT overpayment relief is a specific mechanism for doing exactly that, as confirmed by recent tribunal decisions, including the Upper Tribunal's ruling in BTR Core Fund JPUT v HMRC [2026].

Common Grounds for Disputing a Property Tax Assessment

Understanding why HMRC has issued an assessment is the first step toward challenging it effectively. Common grounds for dispute include:

Valuation disagreements. Capital gains tax depends heavily on the correct valuation of a property, both at acquisition and disposal. HMRC frequently uses its own valuers from the Valuation Office Agency (VOA) and may reach a different figure from the one you used. If you can evidence a better-supported valuation, this is a strong basis for challenge.

Incorrectly applied tax reliefs. A significant number of property tax disputes arise from disagreements over whether a particular relief applies. For CGT, this might include Private Residence Relief, lettings relief, or principal private residence elections. For SDLT, common disputed reliefs include multiple dwellings relief, first-time buyer relief, and mixed-use property treatment.

Errors in HMRC's calculation. HMRC can make factual errors in assessments, including misidentifying the transaction date, the parties involved, or the value of deductible costs. Where the assessment contains a factual mistake, this is a straightforward basis for challenge.

Incorrect categorisation of income. A recurring area of dispute concerns whether profits from property activity are trading income or investment income, as the tax treatment differs significantly. For property developers in particular, the line between CGT and income tax is not always clear, and HMRC does not always get it right.

Discovery assessments raised outside the normal time limits. HMRC's power to raise a tax assessment is subject to time limits. An ordinary discovery assessment for an inaccuracy must normally be raised within four years, extending to six years for careless behaviour and twenty years for deliberate non-disclosure. If HMRC has raised an assessment outside the applicable window, this provides a technical ground for challenge.

Step-by-Step: How to Challenge a Property Tax Assessment

Step 1: Understand Exactly What HMRC Is Claiming

Read the assessment notice carefully. Identify the tax involved, the period it covers, the amount HMRC is claiming, and the stated reason for the assessment. Where HMRC has raised a discovery assessment, the notice should explain the basis on which it believes a discovery was made. Check whether you have been given a right of appeal and note the deadline on the notice.

Step 2: Gather Your Evidence

The strength of a property tax appeal rests on evidence. Depending on the type of dispute, this might include:

• Professional property valuations, ideally from an RICS-qualified surveyor.
• Solicitor's completion statements and conveyancing correspondence for the transaction.
• Records of acquisition costs and improvement expenditure.
• Evidence supporting a claimed relief, such as occupation records for Private Residence Relief.
• Accountancy records and tax returns showing how the figures were calculated.

Collecting this material early, before HMRC's position has hardened further, gives you the strongest possible foundation.

Step 3: Consider Applying for Postponement of the Disputed Tax

For CGT, income tax, and corporation tax disputes, you can apply to HMRC to postpone payment of the disputed amount while your appeal is in progress. This prevents the need to pay a potentially incorrect assessment and then seek a refund later, and suspends debt collection action on the disputed sum.

Postponement is not automatic. You must apply when making your appeal and satisfy HMRC that there are reasonable grounds for believing the assessment is excessive. It's important to address this at the outset rather than after an enforcement notice arrives.

Step 4: File Your Appeal Within 30 Days

For most property tax assessments, the deadline to lodge a formal appeal is 30 days from the date on HMRC's assessment notice. Your appeal should be submitted in writing, clearly identifying what you're disputing and why, and including copies of any supporting evidence you've gathered.

The GOV.UK guidance on disagreeing with a tax decision sets out how to notify HMRC of your appeal and what information your notice should contain. Missing the 30-day window doesn't necessarily close the door, but late appeals require a separate explanation of the delay and are accepted at HMRC's discretion.

Step 5: Pursue a Statutory Review

If HMRC doesn't uphold your appeal following their initial review, you can request a statutory review by an independent HMRC officer with no previous involvement in your case. A review must typically be requested within 30 days of HMRC's rejection. It costs nothing and provides a genuine second look at the matter, without the formality or cost of tribunal proceedings.

Step 6: Claim Overpayment Relief Where Applicable

For SDLT disputes where you believe you've paid more than was legally required, overpayment relief is the relevant mechanism once the standard 12-month amendment window has closed. A claim can be made within four years of the effective date of the transaction using Form SDLT7, setting out the original transaction, the basis of the overpayment, and the amount you're reclaiming.

Overpayment relief claims are sometimes rejected by HMRC and can themselves be appealed to the First-tier Tax Tribunal. This area has been actively litigated in recent years, making it one where specialist advice is particularly valuable.

Step 7: Appeal to the First-tier Tax Tribunal

If a statutory review still doesn't resolve the dispute, the next step is an appeal to the First-Tier Tax Tribunal. This is an independent judicial body with full authority to overturn an HMRC assessment. The tribunal will consider the evidence, hear legal argument from both sides, and issue a binding decision.

Property tax cases at tribunal often turn on valuation evidence and the correct legal interpretation of relieving provisions. They tend to require thorough preparation and, in many cases, expert witness evidence from a qualified surveyor or accountant alongside legal representation.

When to Seek Specialist Help

A straightforward factual correction to a property tax assessment, where the error is clear and well evidenced, can sometimes be resolved through direct correspondence with HMRC. But for anything more complex, specialist input from a tax barrister with property tax expertise makes a material difference.

This is particularly true where:

• The dispute turns on a technical point of law, such as the availability of an SDLT relief or the correct CGT treatment of a development profit.
• HMRC's assessment is based on a valuation you disagree with, and you need a strategy for challenging it.
• The sums at stake are significant relative to the cost of representation.
• HMRC has raised a discovery assessment that may itself be out of time or improperly founded.
• Tribunal proceedings are a realistic prospect, and your case needs careful structuring.

Early specialist advice is rarely wasted in property tax disputes. The way an appeal is framed from the outset, and the evidence gathered to support it, often determines the outcome.

Key Takeaways

Disputing a property tax assessment is a structured process with clear routes at every stage, from a direct appeal to HMRC through statutory review and, if necessary, tribunal. The most important steps are acting within the 30-day appeal window, applying for postponement of the disputed tax where appropriate, and building your challenge on solid evidence and a clear legal basis. The Low Incomes Tax Reform Group's guidance on appealing tax decisions is a useful independent resource for understanding your rights throughout the process.

Frequently Asked Questions

How do I know if an HMRC property tax assessment is wrong?

Start by comparing HMRC's figures against your own records, the valuation used, the costs you deducted, and any reliefs you claimed. If the assessment uses a different valuation, applies a different tax treatment, or ignores costs and reliefs you're entitled to, those are all potential grounds for dispute. A specialist tax adviser or barrister can give you an objective view of whether HMRC's position is sustainable and how strong your grounds for challenge are.

Can I appeal an SDLT assessment if I think I overpaid stamp duty?

Yes. If you believe you applied the wrong rate or failed to claim a relief you were entitled to, you may be able to amend your SDLT return within 12 months of the filing date. After that window, overpayment relief under Schedule 11A Finance Act 2003 is the correct route, allowing claims within four years of the transaction. If HMRC rejects your overpayment relief claim, that decision can itself be appealed to the First-Tier Tax Tribunal.

Do I have to pay a disputed property tax assessment while my appeal is in progress?

Not necessarily. For CGT, income tax, and corporation tax assessments, you can apply to HMRC to postpone payment of the disputed amount pending the outcome of your appeal. Postponement suspends collection action on the sum in dispute. You must apply at the time you lodge your appeal and provide grounds for believing the assessment is excessive. SDLT operates differently, and specific advice is worth taking on the payment position in SDLT disputes.

Received a property tax assessment you want to challenge? Property tax disputes involve technical legal and valuation issues that can significantly affect the outcome. Andy Wood provides specialist advice and representation at every stage, from the initial appeal through to tribunal.

Andy Wood is a specialist Tax Barrister advising property investors, developers, and individuals across the UK on CGT disputes, SDLT challenges, and HMRC assessments.