Appealing HMRC On Rental Income: A Landlord's Guide

A letter from HMRC about your rental income has landed, and your stomach has dropped. It might be a Let Property Campaign letter saying HMRC believes you have undeclared rent. It might be a discovery assessment demanding tax on back years you thought were long closed. Or it might be an enquiry picking apart the expenses you claimed.

Take a breath. You are very likely an "accidental landlord"—someone who inherited a house, kept a former home after moving in with a partner, or let a flat they couldn't sell. You are not the only one, and most people in your position owe far less than they fear once expenses and allowances land, provided they engage with HMRC and get one question right: was the failure careless or deliberate?

This article is about letting a dedicated property—a flat or house you rent out. If your letter is really about short lets of a spare room, an Airbnb in your own home, or selling on a platform, the rules are different and our guide to online-platform income and nudge letters is the better fit. Here we deal with the landlord's lane: how rental income is taxed, the expenses HMRC disputes, the mortgage-interest shock, and how to challenge an assessment or penalty.

How Rental Income Is Actually Taxed

Letting property is taxed as a property business under Part 3 of the Income Tax (Trading and Other Income) Act 2005 (ITTOIA 2005). You do not need to set up a company or register a business name—if you receive rent from UK land, you have a UK property business in the eyes of the law, and the profit is taxable.

The taxable figure is profit, not rent. You take the rents you received and deduct your allowable expenses. A landlord taking £12,000 in rent with £4,000 of genuine costs is taxed on £8,000, not £12,000. This matters enormously when an HMRC letter quotes a scary number—that number is usually gross rent, and your real liability is smaller.

For almost every one- or two-property landlord, the cash basis applies automatically. Introduced as the default for individual landlords from the 2017-18 tax year, it means you tax rent when it lands in your bank account and deduct expenses when you actually pay them—no complicated accounting. You only have to use the more formal accruals basis (known as GAAP) if your cash receipts exceed £150,000 a year, or in a handful of other situations, or if you positively elect for it (s.271A ITTOIA). If you have never heard the term "cash basis," that is fine—it is the simple default, and it is probably what you are already on.

The Expenses HMRC Disputes

Most enquiries into a landlord's return come down to expenses—either which ones you can deduct, or how much. The gateway rule is the wholly-and-exclusively test: an expense is only deductible if it was incurred wholly and exclusively for the purposes of the property business (s.34 ITTOIA, applied to property businesses by s.272). A repair to the let flat qualifies; the portion of a phone bill that is really personal does not.

Two areas cause almost all the trouble: the line between a repair and an improvement, and the mortgage-interest restriction.

Repairs Or Improvements?

This is the classic landlord dispute. A repair—restoring something to its original condition—is a deductible expense. An improvement—making the property better than it was, or creating something new—is capital, and capital expenditure is not deductible against your rental income (s.33 ITTOIA). It may instead reduce a future capital gain when you sell, but it does not cut this year's income tax bill.

The practical test is like-for-like. Replacing a broken tile with a similar tile, repainting, fixing a boiler, mending a fence—those are repairs. Using modern materials that do the same job (double glazing for single-glazed windows, plastic guttering for old metal) is still a repair, because the function is the same even if the materials have moved on. HMRC accepts this in its Property Income Manual at PIM2025. It tips into capital when you make the property better or bigger—a new extension, a fitted kitchen where there was none, converting a loft. HMRC sets the boundary out in PIM2030.

There is one trap worth knowing. If you buy a property that is run-down and not usable until you fix it, that initial work is often capital, not a repair—the courts treat it as part of the price you paid, because you bought it cheap precisely because it needed the work. The courts drew this line a century ago in cases like Law Shipping and Odeon Associated Theatres, and HMRC's guidance at PIM2030 and its Business Income Manual at BIM35450 follows them. The distinction: where the price was knocked down because the property was dilapidated, the first repairs are capital; where the property was usable when bought and the price was not reduced for disrepair, deferred repairs can still be revenue. If HMRC is recharacterising your first-year refurbishment as capital, this is the battleground—and your evidence about the property's condition and the price you paid is what decides it.

The Mortgage Interest Shock

If your real complaint is "why is my tax bill suddenly so high when my rent hasn't changed?", this is almost certainly the answer—and it catches thousands of landlords every year.

It used to be that mortgage interest on a let property was a straightforward deductible expense: £8,000 of interest came straight off your rental profit. That changed. Since the 2020-21 tax year, you can deduct no mortgage interest from residential rental profit (s.272A ITTOIA). The relief was phased out in stages—75% of interest still deductible in 2017-18, 50% in 2018-19, 25% in 2019-20, and nothing from 2020-21.

Instead, you get a basic-rate tax reducer: a credit worth 20% of your finance costs, knocked off your final tax bill rather than off your profit (s.274A and s.274AA ITTOIA).

Here is why it bites. Take a higher-rate landlord with £8,000 of mortgage interest:

• Old rules: deduct £8,000 from profit; at the 40% rate that saved £3,200 of tax.
• Now: the full rent is taxed with no interest deduction, and you get a credit of 20% × £8,000 = £1,600.

The £8,000 interest still leaves your bank account, but you only get £1,600 of relief instead of £3,200. For a basic-rate taxpayer the change is broadly neutral; for a higher-rate landlord it roughly halves the value of the relief.

There is a second sting. Because the full rent now sits in your taxable income (with relief coming off afterwards as a credit), your total income figure is higher than it used to be. That can tip you into the higher-rate band, taper away your personal allowance, or push you over the £60,000 threshold for the High Income Child Benefit Charge. A landlord who never thought of themselves as a "higher earner" can find rental property has quietly made them one.

One change is on the horizon but not yet in force: legislation provides for the credit to be calculated at a new "property basic rate" from the 2027-28 tax year onwards. For now—2026-27 and earlier—the relief is at the basic rate of 20%. Do not assume a different figure for years that have not yet started.

The Allowances That Can Help

Two reliefs can wipe out small rental liabilities entirely.

The property allowance is £1,000 a year (s.783BD ITTOIA). If your gross rental receipts are £1,000 or less, the income is not taxed and you do not have to report it. If they are more, you can choose to deduct the £1,000 allowance instead of your actual expenses—useful only if your real costs were under £1,000, and you cannot claim both. One catch for mortgaged landlords: the property allowance is not available alongside the finance-cost relief, so if you are claiming the 20% mortgage-interest credit, the £1,000 allowance is off the table.

Rent-a-room relief exempts up to £7,500 a year, but only for letting furnished accommodation in your own home—a lodger, or a spare room. It does not apply to a separate let property you do not live in. If two people receive income from the same home, the limit is halved to £3,750 each (s.789 ITTOIA). If your HMRC letter is really about a lodger rather than a buy-to-let, this relief may mean there was never anything to declare.

Who Pays The Tax On Jointly-Owned Property

If you own the property with someone else, who pays the tax on the rent is not always obvious—and HMRC's default can surprise people.

For a married couple or civil partners who live together, the law treats the rental income as belonging to them in equal shares—50/50—no matter what the actual ownership split is (s.836 ITA 2007). So even if one spouse owns 90% of the property and the other 10%, HMRC taxes them 50/50 by default. That can be good news (it spreads income towards a lower earner) or bad news (it pulls income towards a higher earner who would rather not have it).

A couple can switch to taxing the income in line with their actual beneficial shares by filing a declaration—the Form 17 route (s.837 ITA 2007). Two conditions are strict. First, the declared split must match your real beneficial interests in the property—you cannot invent a 90/10 income split if you do not actually hold the property 90/10. Second, the declaration must reach HMRC within 60 days of being made, or it has no effect. HMRC explains the mechanics in PIM1035.

Unmarried co-owners—siblings who inherited a house, an unmarried couple, friends—are not caught by the 50/50 rule at all. Their income follows their beneficial entitlement to it, and co-owners who are not a couple can agree a different split. If HMRC has taxed you on a share you do not think is right, the ownership documents and any agreement between the owners are what decide it.

A Note On Holiday Lets

If your property is a holiday let, the rules changed sharply on 6 April 2025. The special furnished holiday lettings regime—which gave holiday lets capital allowances, certain capital-gains reliefs, and their own treatment for couples—was abolished by Finance Act 2025, section 25 and Schedule 5.

From 6 April 2025, a former holiday let is taxed like any other residential let: the mortgage-interest restriction applies, the old capital allowances on furniture are gone, and married-couple owners revert to the 50/50 default unless they file Form 17.

The crucial point for an appeal is which tax year HMRC is assessing. If the dispute is about 2024-25 or earlier, the old holiday-let rules apply. If it is 2025-26 onwards, the new rules apply. The date of the tax year decides everything here.

"I Didn't Declare My Rent": Disclosure And Discovery

If your letter is a nudge or a back-years assessment because you never told HMRC about the rent, this section is for you. The good news is that engaging early and honestly almost always produces a better outcome than waiting. The thing that decides how bad it gets is behaviour.

And to answer the fear most people will not say out loud: this is a civil process, not a criminal one. The penalties in this article are tax-geared percentages, not prosecutions—HMRC reserves criminal investigation for the most serious fraud, and coming forward voluntarily through a disclosure facility is precisely the route HMRC wants ordinary landlords to take. An accidental landlord who engages and discloses is dealt with in pounds, not in court.

Telling HMRC Late

If you receive taxable rental income and HMRC has not sent you a tax return to complete, you have a legal duty to notify them. Under section 7 of the Taxes Management Act 1970, you must do this by 5 October following the end of the tax year in which the income arose. Miss that, and you have a "failure to notify"—which carries its own penalty under Schedule 41 of the Finance Act 2008, and, as we will see, opens up a much longer window for HMRC to reach back.

Going forward, "declaring" has a concrete meaning: you register for Self Assessment and report the rent each year on the SA105 (UK property) pages of your tax return. Sorting out the past and getting the current year onto a return are two halves of the same fix.

The Let Property Campaign

HMRC's Let Property Campaign is a voluntary disclosure route for individual landlords of residential property. The mechanics are simple: you notify HMRC that you intend to disclose, and you then have 90 days to work out and pay what you owe. The terms—particularly the penalty—are usually better than if HMRC catches up with you first, and HMRC provides a calculator that covers up to 20 years. If you are not sure whether you even need to disclose, GOV.UK has a short eligibility checker that walks you through it.

If you cannot pay everything at once, that is not a reason to stay silent. HMRC can agree a Time to Pay instalment arrangement, and the campaign accommodates payment proposals—what matters is disclosing and engaging, not producing the whole sum on day one.

There is one limit worth understanding, because it shapes what the tribunal can do for you. The campaign's favourable terms are an administrative concession—HMRC's own practice—not a statutory entitlement. So the First-tier Tribunal cannot order HMRC to apply the campaign or review how HMRC handled it on "fairness" grounds; the tribunal is a creature of statute, and "be fair to me" is a complaint or judicial-review matter. Our analysis of Hok v HMRC explains where that line falls. What the tribunal can do is hear an appeal against the resulting assessment (the amount, the time limits, whether there was even a property business) and against the penalty (the behaviour, reasonable excuse, special reduction)—and those are real, winnable arguments.

How HMRC Already Knows

Many landlords assume a nudge letter is a guess or a bluff. It usually is not—HMRC has a wide net of data, and its Connect system cross-matches it.

Letting and estate agents are required to hand over data about the rents they collect under Schedule 23 of the Finance Act 2011, and HMRC can demand it in bulk, not just for one named taxpayer. On top of that it draws on tenancy deposit scheme records, Land Registry ownership data, council licensing and HMO registers, mortgage and electoral-roll data, and platform data for short lets. By the time the letter arrives, HMRC very often already knows you have a let property. It is an invitation to come forward on better terms—not a fishing expedition you can ignore.

Ignoring it has a concrete cost. HMRC can simply raise its own estimated assessment from the data it holds—usually a worse number than your real one, because it knows your gross rent but not your expenses—and once HMRC has contacted you, any disclosure you make is prompted, which carries a higher penalty floor than coming forward unprompted.

Behaviour, Back-Years And Penalties

This is the single most important part of the whole article. Behaviour—careless versus deliberate—drives everything: the penalty band, how many years HMRC can reach back, and whether the presumption of continuity sweeps in a decade. Expenses reduce the number you owe; behaviour decides the scope and the danger.

The failure-to-notify penalty under Schedule 41 is a percentage of the tax that went unpaid, set by behaviour:

• Non-deliberate—up to 30%
• Deliberate but not concealed—up to 70%
• Deliberate and concealed—up to 100%

Those percentages are reduced for the quality of your disclosure, and an unprompted disclosure (you came forward before HMRC contacted you) attracts a lower floor than a prompted one (after a nudge letter). Our guides to reducing HMRC penalties and HMRC penalties explained cover the bands and mitigation in detail.

The same behaviour question sets how far back HMRC can go:

• Reasonable care taken—4 years (s.34 TMA)
• Careless—6 years (s.36(1) TMA)
• Deliberate, or a failure to notify—20 years (s.36(1A) TMA)
• Offshore matters—12 years (s.36A TMA), within the 20 years deliberate ceiling

So a landlord who registered for Self Assessment on time and simply made a mistake faces four years; one who never told HMRC at all can be reached for up to twenty. That is why "careless versus deliberate" is the battleground, and why a finding of deliberate behaviour—which, after the Supreme Court in Tooth v HMRC, means an intention to mislead—is so dangerous. It is not a label to accept lightly.

Budget for interest too. Late-payment interest—currently 7.75%—runs on each year's unpaid tax from the date it was originally due, so on ten or fifteen back-years it can rival the tax itself. Interest is not a penalty: it is not reduced for co-operation, and there is no right of appeal against it. The real exposure is always tax + interest + penalty—our guide to interest on unpaid tax explains how it is calculated.

One more mechanism to know about: the presumption of continuity. Where HMRC proves you under-declared rent in one year, it commonly assesses the surrounding years on the basis that the same situation is presumed to continue until you show it changed—and the onus of showing the change is on you. In practice, HMRC finds two undeclared years and assesses ten. The presumption is rebuttable and has limits—HMRC still needs an evidential basis, and it expresses no rigid legal rule—but rebutting it takes records. Our guide to discovery assessments explains how HMRC reopens closed years and how the split burden works.

Two Real Cases

Two recent tribunal decisions show how undeclared-rent appeals actually play out—and why evidence and engagement matter more than a good story.

In Herrmann v HMRC [2024] UKFTT 303 (TC), a landlord with undeclared rent from three properties faced discovery assessments and failure-to-notify penalties, with HMRC reaching back twenty years on the basis that the failure to notify was negligent. His defence was that he had relied on an estate agent—who had since died—to handle his tax. The tribunal applied the four-step reasonable-excuse test from Perrin v HMRC and found that relying on the agent was not, objectively, a reasonable excuse. The assessments and penalties stood. This is the archetypal "I thought the agent dealt with it" case, and it usually fails.

In Locke v HMRC [2025] UKFTT 956 (TC), a landlord with rent from two properties argued that a 2007 letter from HMRC had told him he did not need to file returns. The tribunal rejected this: the duty to notify applies to all taxable income, not only where a profit is made, and HMRC's silence does not remove the duty. The failure was found to be deliberate, and the penalties were upheld. The "HMRC told me I didn't need to file" defence, defeated.

The lesson from both is consistent. Weak excuses—an agent who let you down, a half-remembered conversation, "I didn't think I owed anything because there was a mortgage"—rarely win. What wins is evidence: bank statements, tenancy agreements, agent statements, and invoices showing a repair was a repair. The strongest position is the landlord who engages early, produces records, and argues the right number rather than relying on a story.

How To Challenge An Assessment Or Penalty

If HMRC raises an assessment or penalty you think is wrong, you have full appeal rights (s.31 TMA). The route is the same as for any HMRC dispute, and it has a strict clock.

You appeal in writing within 30 days of the decision. You can then ask for a free HMRC statutory review by a different officer—completed within 45 days—and, whether or not you take the review, you can appeal to the First-tier Tribunal, where there is no fee to do so. If the 30-day window has already passed, a late appeal is still possible, but the tribunal applies a strict test and you will need to explain the delay.

Understand what the tribunal can and cannot do. It can decide whether the assessment is valid, whether it is in time, what the correct amount is, and whether a penalty is right. It cannot order HMRC to be lenient, to apply the Let Property Campaign, or to act "fairly" outside the law—that is the Hok limit again.

The burden of proof is split, and knowing which way it falls shapes your case:

• On the amount of an assessment, the burden is on you to show it is excessive (s.50(6) TMA). This is where your records do the work—produce the real rents and the real expenses, and the estimate falls away.
• On the validity of a discovery assessment, the burden is on HMRC to show the conditions were met and that it acted in time. See our guides to discovery assessments, Wilkes and Tinkler for how those conditions are tested.
• On a penalty, the burden is on HMRC to establish the behaviour—careless, deliberate, concealed—before any penalty bites.

Against a penalty, you may also have a reasonable excuse. This is a defence to the penalty, not the tax, and the tribunal applies the four-step test from Perrin—see also our guide to what counts as a reasonable excuse. Be realistic: "I didn't know rent was taxable" rarely succeeds for someone who knew perfectly well they were receiving rent. For structuring the whole thing, our guides to writing grounds of appeal, your HMRC appeal rights, and HMRC enquiries and closure notices walk through each step.

Overseas Property And Making Tax Digital

Two things to flag, briefly, with signposts to fuller guides.

Overseas property is a separate property business in law (s.265 ITTOIA)—foreign rental profits do not pool with your UK ones. If you are a UK resident, your foreign rent is taxable here (with relief for foreign tax paid), and undeclared foreign rent engages the longer 12 years offshore time limit. Critically, the right disclosure route is not the Let Property Campaign but the Worldwide Disclosure Facility. If you have a flat abroad, our guide to offshore disclosure and penalties is where to go.

Making Tax Digital for Income Tax is coming for landlords. If your gross rents (plus any sole-trade turnover) exceed £50,000, you are mandated into digital record-keeping and quarterly updates from 6 April 2026; the threshold drops to £30,000 in 2027 and £20,000 in 2028. The trap is the word gross: the £50,000 is measured on rent before expenses and before mortgage interest, so a landlord with a big mortgage and a small profit can still be caught. Our guide to Making Tax Digital for Income Tax covers the detail.

And two more handoffs for completeness: when you eventually sell a residential property, a separate 60-day reporting and payment regime applies—see CGT 60-day reporting appeals. If you bought through a company or paid the wrong rate, SDLT appeals is the place to start. And if you hold the property through a limited company, the tax and appeal rules are different again—see corporation tax appeals.

What To Do Now

1. Gather your records. Bank statements, tenancy agreements, letting-agent statements, and invoices for repairs. These do two jobs: they prove the real figures (cutting any estimate down to size) and they show a repair was a repair, not capital.
2. Work out the real number. Rent minus allowable expenses—and remember the mortgage-interest credit and any £1,000 property allowance. Then add late-payment interest on each back year. Most accidental landlords owe less than the letter implies, but the honest total is tax plus interest plus penalty.
3. Decide on the Let Property Campaign versus waiting. Coming forward voluntarily usually means a lower penalty than letting HMRC catch up—and a prompted disclosure carries a higher floor than an unprompted one.
4. Get the behaviour question right. Careless or deliberate is the master variable—it sets the penalty band and how many years HMRC can reach. Do not accept a "deliberate" label without thinking hard about whether it is justified.
5. Appeal in time. You have 30 days from the decision. Diary it, ask for a statutory review if you want a second look, and use a late appeal only if you have to.
6. Get help if you are unsure. A Chartered Tax Adviser or accountant can be engaged for a single piece of work, and free help is available from TaxAid (taxaid.org.uk) and the Low Incomes Tax Reform Group (litrg.org.uk).

For the wider picture of how any HMRC dispute unfolds, see our tax dispute timeline.

Key Legislation And Resources

Legislation

• Sections 264-265, ITTOIA 2005—UK and overseas property businesses
• Section 271A, ITTOIA 2005—the cash basis and the £150,000 threshold
• Sections 34 and 272, ITTOIA 2005—the wholly-and-exclusively test for expenses
• Section 272A, ITTOIA 2005 and sections 274A / 274AA—the finance-cost restriction and the basic-rate reducer
• Section 783BD, ITTOIA 2005—the £1,000 property allowance
• Section 789, ITTOIA 2005—rent-a-room relief (£7,500)
• Sections 836 and 837, ITA 2007—the 50/50 default for couples and the Form 17 route
• Finance Act 2025, section 25—abolition of the furnished holiday lettings regime
• Section 7, TMA 1970—duty to notify chargeability by 5 October
• Sections 31, 34, 36 and 36A, TMA 1970—right of appeal and assessment time limits
• Section 50(6), TMA 1970—burden of proof on the amount
• Schedule 41, Finance Act 2008—failure-to-notify penalties
• Schedule 23, Finance Act 2011—HMRC's data-gathering powers over letting agents

GOV.UK Guidance

• Property Income Manual PIM2025 and PIM2030—repairs versus capital improvements
• Property Income Manual PIM2054—the finance-cost (mortgage interest) restriction
• Property Income Manual PIM1035—jointly owned property and Form 17
• Business Income Manual BIM35450—property bought in a defective condition
• Let Property Campaign: your guide to making a disclosure
• Check if you need to tell HMRC about your rental income
• SA105: UK property pages for Self Assessment
• Abolition of the furnished holiday lettings tax regime

On This Site

• Online-platform income and nudge letters—spare rooms, Airbnb and short lets
• Discovery assessments—how HMRC reopens closed years
• HMRC enquiries and closure notices
• Wilkes v HMRC and Tinkler v HMRC—when a discovery assessment is valid
• Tooth v HMRC—what "deliberate" means
• Hok v HMRC—why the tribunal cannot order HMRC to "be fair"
• HMRC penalties explained, reducing HMRC penalties and self-assessment penalties
• Interest on unpaid tax—it runs from each year's original due date and cannot be appealed
• What is a reasonable excuse? and Perrin v HMRC
• The High Income Child Benefit Charge—the finance-cost restriction can tip you into it
• Offshore disclosure and penalties—for overseas property
• Making Tax Digital for Income Tax—coming for landlords from April 2026
• Understanding your HMRC appeal rights, HMRC internal review, how to appeal to the tax tribunal, writing grounds of appeal and late appeal to the tax tribunal
• CGT 60-day reporting appeals (when you sell), SDLT appeals (on purchase) and corporation tax appeals (company landlords)
• Tax dispute timeline

This article is for informational purposes only and does not constitute legal or tax advice. For advice specific to your situation, consult a qualified tax adviser, accountant, or solicitor.