If HMRC has never heard about some or all of your rental income, the Let Property Campaign is the mechanism built specifically to fix that. It gives residential landlords a formal way to bring past tax years up to date — and, more often than not, it’s simply a question of when you report it rather than whether HMRC eventually finds out on its own.
This guide covers how HMRC actually identifies undisclosed rental income, who the campaign is open to, the exact steps involved in making a disclosure, and what happens if HMRC pushes back on your figures.
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How HMRC Actually Finds Undisclosed Rental Income
It’s tempting to assume small or informal lettings fly under the radar. In practice, HMRC pulls from a wide net of sources: letting agent records, land registry filings, council tax data, mortgage applications, and even reports from members of the public. Where the data points to rental income that hasn’t been matched against a tax return, HMRC will often reach out directly, inviting the landlord to use the Let Property Campaign to put things right.
The key detail here is timing. You don’t have to wait for that letter. Landlords who register for the campaign proactively — before any contact from HMRC — are treated more favourably, with faster resolution and materially lower penalties than those who only respond once HMRC has already made contact.
Who the Campaign Is Open To
The Let Property Campaign covers a broad range of residential landlords, including:
- Landlords with one or more residential properties, whether in the UK or overseas
- Individuals renting out a room in their own home under the Rent a Room Scheme
- Landlords letting to students, workforce tenants, or similar groups
- Holiday let landlords
Who Can’t Use It
A few situations fall outside the scope of the campaign:
- Commercial property — shops, garages, and lock-ups aren’t covered on their own, though a mixed portfolio with a residential component can still use the campaign for that portion
- Companies and trusts — these need to use a different disclosure route entirely; the campaign is for individuals
- Directors and commercial landlords — separate disclosure methods apply here too
Joint ownership is treated individually, not jointly. Where a property is owned by more than one person, each owner needs to make their own separate disclosure covering their share of the profit — a single combined submission isn’t accepted.
The Disclosure Process
1. Notify HMRC of your intent If HMRC hasn’t already been in touch, you register your intention to disclose and receive a reference number in return.
2. Quantify the undisclosed income Within 90 days of getting that reference number, work out all previously undisclosed income and gains across every year HMRC can still assess — and this isn’t limited to rental income alone; any other undisclosed business or investment income within scope should be included too.
3. Calculate what’s owed Work through the additional tax, interest, and penalties due for each affected tax year.
4. Make a formal offer Submit a formal offer to HMRC to settle everything in full and final settlement of your historical position.
5. Pay using your reference number Once the offer is submitted, use your Payment Reference Number to settle the agreed amount.
6. Submit full supporting detail Alongside your calculations and offer, provide a comprehensive account of the facts and assumptions behind your figures.
What happens after submission: HMRC typically sends an acknowledgement within around two weeks, followed by internal checks. If they’re satisfied, you’ll receive a formal acceptance letter closing the matter. If not, expect follow-up questions aimed at verifying your figures.
Going forward, staying compliant means registering for Self Assessment if you haven’t already, and reporting all income and gains through your annual return from that point on.
There’s real value in professional input at this stage — not just to get the numbers right, but because there are legitimate technical arguments that can reduce both the number of years included and the resulting penalty. For a closer look at how everyday situations turn into undisclosed income in the first place, our article on common landlord tax errors is worth reading alongside this one.
How Many Years Get Included
The number of assessable years isn’t fixed — it depends on the nature of the underlying issue, and our guide on which years you need to declare covers this in full detail.
One point worth flagging clearly: if income or gains were deliberately left off a return, there’s a genuine risk of prosecution, and professional advice on your options is strongly recommended before proceeding. In cases involving deliberate conduct, the Contractual Disclosure Facility is a separate route that can offer immunity from prosecution — a very different mechanism from the Let Property Campaign, and one worth discussing with an advisor if it’s relevant to your circumstances.
What If Your Records Are Incomplete?
Missing historical records don’t remove the obligation to disclose. The expectation is a genuine effort to obtain what documentation still exists, and where gaps remain, reasonable, well-explained assumptions can be used to quantify the income and gains involved.
How the Tax Is Actually Calculated
Tax on previously undeclared profit is worked out using the rates and allowances that applied in each specific tax year in question — not current-year rates applied retrospectively. How much falls due depends on how far income sat above the tax-free personal allowance for that year, and it’s worth making sure every available relief is claimed rather than assumed away.
How the Penalty Is Set
Penalty rates vary by circumstance, but voluntary, high-quality disclosures consistently land at the lower end of the scale. The starting point also differs depending on whether returns were filed incorrectly versus never filed at all.
HMRC reduces penalties based on how the disclosure is handled — often summarised as telling, helping, and giving: coming forward with the issue, actively assisting HMRC in understanding it, and cooperating fully in establishing the correct figures. Landlords weighing up the practical cost difference between disclosing voluntarily and waiting to be contacted may find our voluntary disclosure guide useful, since it walks through real penalty comparisons with worked figures.
If HMRC Disagrees With Your Disclosure
HMRC retains the right to review any disclosure for accuracy and can challenge the assumptions behind it, including requesting the underlying records used to support the figures submitted.
Where a disagreement over the final amount can’t be resolved, HMRC may issue formal assessments for the tax and penalties it believes are due. From there, you retain the right to appeal. If an appeal doesn’t resolve things, further options remain available — including requesting an internal review or taking the matter to the Tax Tribunal for a final decision.
Getting It Right From the Start
A well-prepared disclosure, backed by accurate figures and a clear explanation of the facts, is far more likely to close quickly and without dispute. Given the technical judgement involved in scoping the right years and minimising penalties, most landlords benefit from working through this with an experienced advisor rather than navigating it alone. For the full picture on eligibility and process, our complete Let Property Campaign guide brings everything together in one place.
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