HMRC Penalties for Undeclared Rental Income: The Complete Guide

The penalty on undeclared rental income is often the most negotiable part of an HMRC settlement. Understanding how penalties are calculated, what determines the percentage applied and how to argue for reductions is therefore one of the most practically valuable things a specialist can do for you.

The legal framework: Schedule 24 and Schedule 41

Two penalty regimes apply to landlords depending on the nature of the failure:

• Schedule 24, Finance Act 2007 , applies to inaccuracies in returns or documents submitted to HMRC. This covers errors in a Self Assessment return, such as understating rental income or overclaiming expenses.
• Schedule 41, Finance Act 2008 , applies to failure to notify HMRC of a chargeability to tax. This covers landlords who were not registered for Self Assessment and did not notify HMRC that they had rental income to declare.

The two regimes have different mechanics but broadly similar penalty ranges. Most rental income cases involve one or both.

How behaviour is assessed

Both Schedule 24 and Schedule 41 penalties are calibrated by reference to the taxpayer’s behaviour. There are three categories:

• Careless , a failure to take reasonable care. The taxpayer should have known better, but there was no intention to deceive.
• Deliberate , the taxpayer knew that the return was incorrect (or knew that they should have notified HMRC) and chose not to correct it.
• Deliberate and concealed , not only was the omission deliberate, but steps were taken to conceal it: separate bank accounts for rental income, deliberately omitting properties from records shown to an accountant, providing false information during an enquiry.

HMRC investigators are trained to look for evidence that elevates behaviour from careless to deliberate. The longer the period of non-declaration, the harder it is to maintain a “careless” argument, particularly where the landlord was otherwise sophisticated about their financial affairs. A portfolio landlord of fifteen years who has never mentioned rental income to HMRC will find the “careless” argument difficult.

Common behaviour arguments for landlords

“I didn’t know I had to declare it”

This is the most frequently stated reason for non-declaration, and it is not automatically an answer. The question HMRC asks is not whether the taxpayer subjectively knew, but whether a taxpayer exercising reasonable care would have known. A landlord who receives regular monthly payments to a bank account, for letting a property they own, will find it difficult to argue they did not know this was income. They might more realistically argue that they did not know which tax form to use or that they misunderstood the Rent-a-Room scheme threshold as applying to all lettings.

The argument is stronger where the landlord was a first-time accidental landlord (for example, someone who inherited a property and let it briefly before selling), had no prior tax complexity in their affairs and genuinely had no reason to engage with Self Assessment before. In those circumstances, “careless” rather than “deliberate” is a supportable position.

“My accountant handled it”

Agent error is a recognised form of mitigation under Schedule 24. Paragraph 18 of Schedule 24 FA 2007 provides that where an inaccuracy arose because the taxpayer relied on an agent, the penalty is determined by reference to the taxpayer’s own behaviour, but only if the taxpayer provided accurate and complete information to the agent. If the landlord told the accountant about all their properties and the accountant omitted one from the return, that is an agent error and the landlord’s behaviour is likely to be careless rather than deliberate.

If, however, the landlord failed to mention a property to the accountant or provided figures that omitted certain income, agent error provides no defence, because the agent only prepared the return based on what the landlord told them. The “my accountant handled it” argument works best where there is clear documentary evidence of what information was provided to the accountant.

Penalty ranges for landlord cases

The following ranges apply under both Schedule 24 (inaccuracies) and Schedule 41 (failure to notify), in domestic (UK-source) cases:

Within each range, HMRC must reduce the penalty to reflect the quality of disclosure. The three “quality” elements are:

• Telling: proactively bringing the inaccuracy to HMRC’s attention
• Helping: assisting HMRC quantify the liability by providing records and calculations
• Giving access: providing access to records and information when requested

Each element contributes to the reduction from the maximum of the range toward the minimum. A taxpayer who proactively notified HMRC, provided complete and well-organised records and raised no spurious challenges to figures is entitled to a penalty at or very close to the bottom of the applicable range.

Interest on underpaid tax

In addition to the penalty, HMRC charges interest on unpaid tax from the date it was originally due. For income tax, the due date is generally 31 January following the tax year, so for 2019/20 income tax, interest has been running since 31 January 2021. The current HMRC interest rate on underpaid tax is linked to the Bank of England base rate plus 2.5 percentage points. With base rate at elevated levels compared to the pre-2022 norm, interest adds a material sum for older years.

For a £10,000 income tax liability from 2019/20 that is settled in mid-2026, the interest element at current rates is approximately £2,800, before any penalty is added. Interest is not negotiable, it runs automatically by statute. Only the penalty is subject to mitigation and negotiation.

Multi-year omissions vs current-year errors

A single-year error in a Self Assessment return typically attracts a relatively modest absolute penalty even at high percentage rates, because the tax on one year of rental profit is limited. The financial exposure compounds dramatically once multiple years are involved.

Consider a landlord with £8,000 of net rental profit per year, a marginal rate of 40%, who has been letting without declaring for eight years. The cumulative underpaid income tax is £25,600. At a deliberate prompted penalty of 35%, the penalty is £8,960. Interest on each year’s liability accrues from the relevant January, so the total interest bill (applying current rates and averaging across years) might be around £7,000. The total settlement is approximately £41,560. Had the landlord come forward before receiving an HMRC nudge letter, the unprompted deliberate penalty could have been assessed at 20% minimum, reducing the penalty to £5,120, a saving of £3,840.

The numbers illustrate why acting before HMRC contacts you is financially rational, not just morally correct.

The offshore property uplift

Where undeclared rental income arises from overseas property, the penalty framework is different and more severe. Schedule 24 FA 2007 applies an uplift to penalties for offshore matters based on the “category” of the territory involved:

• Category 1 territories (broadly, territories with full exchange-of-information arrangements with the UK, including most EU countries, the US and Australia): standard penalty ranges apply
• Category 2 territories (territories with partial information exchange): penalty maximums increased by 50% above the domestic range
• Category 3 territories (territories with no information-sharing arrangements with the UK): penalty maximums increased to 200% of the potential lost revenue

In addition, where the territory is a Category 2 or 3 territory and the behaviour is deliberate, HMRC has the power to “name and shame” the taxpayer by publishing their details. This provision is used rarely but exists as an additional deterrent.

Most European holiday lets involve Category 1 territories, so the standard domestic penalty ranges apply. But landlords with property in certain jurisdictions should take specialist advice on the applicable penalty category before making any disclosure.

Appealing HMRC penalty assessments

Every HMRC penalty decision can be appealed. The two-stage process is:

1. Statutory review: a review of the decision by a different HMRC officer, requested within 30 days of the penalty notice and completed by HMRC within 45 days. The review is free and must be exhausted before a Tribunal appeal is possible.
2. First-tier Tax Tribunal: an independent judicial body that considers both the underlying tax liability and the penalty. Tribunal judges assess the evidence independently and are not bound by HMRC’s internal guidance on behaviour categorisation.

Common grounds for appeal in landlord penalty cases include:

• HMRC has categorised behaviour as deliberate when the evidence supports only careless
• HMRC has not given sufficient credit for the quality of disclosure (telling, helping, giving access)
• Reasonable excuse exists, eliminating the penalty entirely
• The underlying tax calculation is incorrect, reducing the “potential lost revenue” on which the penalty percentage is applied

Use our HMRC penalty calculator to model the financial impact of different behaviour categories and disclosure scenarios.

Reasonable excuse for landlords

Section 70 Finance Act 2007 provides that no penalty arises where a person had a “reasonable excuse” for the inaccuracy or failure. Reasonable excuse is a complete defence, it reduces the penalty to nil, not merely to the minimum of the applicable range.

HMRC’s own guidance (CH160000 series in the Compliance Handbook) identifies circumstances that can constitute reasonable excuse. In landlord cases, the following arguments are regularly pursued:

• Reliance on incorrect professional advice: Where a landlord asked their accountant or solicitor whether the rental income needed to be declared and was told incorrectly that it did not, this can be a reasonable excuse, provided the taxpayer gave the adviser all relevant facts and the advice was not obviously wrong.
• Serious illness: Where the taxpayer was incapacitated during the relevant period and genuinely unable to manage their tax affairs.
• Probate delays: Where an inherited property was let during the probate period, before the estate was fully administered and the landlord was formally identified as the owner. This is a genuine grey area and HMRC is generally receptive to it for the earliest years of a disclosure.
• COVID-19 disruption: Limited application for most rental income cases, but relevant where a landlord was unable to access records or professional advice during the lockdown period to address a known discrepancy.

What is specifically not a reasonable excuse, per HMRC guidance and First-tier Tribunal decisions:

• Ignorance of the law, without more
• Pressure of other work or personal commitments
• Financial hardship (which may reduce the penalty itself in some circumstances, but is not a reasonable excuse for the inaccuracy)

Special reduction for good faith disclosures

Paragraph 11 Schedule 24 FA 2007 gives HMRC discretion to reduce a penalty “if they think it right because of special circumstances.” This “special reduction” is intentionally narrow, it is not a general discretion to be lenient. However, it can be invoked where the taxpayer has made a genuinely exceptional disclosure or where the strict application of the penalty would produce a disproportionate result. We have achieved special reductions in cases where the taxpayer voluntarily disclosed assets that HMRC had no independent knowledge of and where the penalty that would otherwise have applied was demonstrably out of proportion to the culpability involved.

Real-world penalty ranges we see at this firm

Drawing on cases across our practice, the following gives a realistic picture of outcomes in Let Property Campaign and related landlord enquiries:

• Accidental landlord, one property, 3–5 years, careless, unprompted LPC disclosure: Penalty 0–5% after quality-of-disclosure credit. In several cases, 0% on a reasonable care or reasonable excuse argument.
• Portfolio landlord, 3–5 properties, 5–8 years, deliberate (no concealment), prompted by nudge letter: Penalty 35–45% after quality-of-disclosure reductions. Occasionally reduced to low 30s where the disclosure was genuinely comprehensive and prompt.
• Long-term landlord, 10+ years, deliberate, prompted by formal enquiry: Penalty 40–60%, depending on the extent of cooperation and the strength of any behaviour re-categorisation argument. The lower end of this range requires active specialist negotiation.
• Overseas property, Category 1 territory, deliberate, unprompted: Standard range, typically 25–35% after reductions. The international element adds complexity but does not automatically increase the penalty where the territory is Category 1.

Related guides in this series

• HMRC rental property investigations: the complete guide
• The Let Property Campaign: disclosure step by step
• When HMRC finds undeclared rental income
• Common rental income Self Assessment errors
• HMRC penalty calculator
• All resources