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Self Assessment

How do I tell HMRC about rental income I never declared, before they find me?

Answered by Jordan Onraet-Wells, Founder & Chartered Tax Adviser (CTA). Published 17 August 2026. Last reviewed 17 August 2026.

The short answer

Use HMRC's Let Property Campaign, the standing voluntary disclosure route for individual landlords with undeclared income from letting residential property, including people living abroad who rent out UK property. You notify HMRC first, then have 90 days from their acknowledgement to disclose every year in scope, self-assess the penalty, make a formal offer and pay. Coming forward before HMRC writes keeps you in the unprompted penalty ranges, often 0% to 10% of the tax, while waiting to be found raises the minimums sharply and invites the argument that your behaviour was deliberate, with prompted penalties running from 35% up to 100%.

  • The campaign is for individuals only: companies, trusts and non-residential lettings such as shops or lock-ups cannot use it, and purely offshore income belongs in the Worldwide Disclosure Facility instead.
  • How many years go in follows behaviour: up to 4 with reasonable care, 6 if careless, and up to 20 where you never told HMRC you were liable, which is the category most landlords who never registered fall into.
  • Disclosing unprompted transforms the penalty: a landlord who never registered and comes forward more than 12 months late sits in a 10% to 30% band and can realistically achieve the 10% floor, against a 20% floor once HMRC prompts and 35% or more if deliberate behaviour is argued.
  • Interest runs daily on every disclosed year from its original due date until payment, at 7.75% a year since 9 January 2026, so hesitation quietly grows the bill across every year at once.
  • The window closes when HMRC's letter lands: a disclosure is unlikely to be accepted into the campaign once an enquiry or compliance check has been notified.

The Let Property Campaign is the route, and it covers non-residents

The Let Property Campaign is HMRC's standing disclosure facility for individuals with undeclared income from letting residential property: a single buy-to-let, a portfolio, a room let above the Rent a Room threshold, a holiday let, an inherited property kept and let, and, expressly, people living abroad for six months or more who rent out UK property. That last group is the commonest case we see: someone moved abroad years ago, kept the flat, and assumed leaving the country ended their UK obligations. It did not, because UK rental income stays UK-taxable however long you are away, as our non-resident landlord guide explains. The campaign is not for companies or trusts, and income from overseas property is an offshore issue for the Worldwide Disclosure Facility instead. If your only problem is a recent filed return with the rent left off, you may not need the campaign at all: a return can usually be amended within 12 months of its filing deadline.

How the process runs and what it costs

The campaign is self-assessed from start to finish. You notify HMRC and receive a disclosure reference, then within 90 days of the acknowledgement you disclose the rental income and allowable expenses for every year in scope, calculate the tax and interest, self-assess the penalty with your behaviour category justified, make a formal offer for the total and pay. The years in scope mirror HMRC's assessment limits: 4 if you took reasonable care, 6 if careless, and up to 20 where you failed to notify or acted deliberately. The penalty is a percentage of the tax lost, and behaviour plus timing decide it: a careless error disclosed unprompted can fall to nil, and non-deliberate failure to notify disclosed unprompted after 12 months carries a 10% to 30% band with the floor achievable through full cooperation. Two things soften many non-resident cases: eligible individuals such as British citizens can still set the Personal Allowance against rental profit, and any basic rate tax already deducted under the Non-resident Landlord Scheme is credited against the bill. The full arithmetic, including a worked six-year example, is in our Let Property Campaign guide.

Why moving before HMRC writes is worth thousands

Once a nudge letter or compliance check notification arrives, three things change at once: the disclosure becomes prompted so every penalty floor rises, years of silence become easier to paint as deliberate, and you lose the campaign's self-assessed process in favour of an enquiry HMRC runs on its own timetable. On six undeclared years the difference between a 10% unprompted settlement and a prompted deliberate argument at 35% or more is measured in thousands of pounds, on identical tax and interest. The same exercise also fixes the future cheaply: Self Assessment registration, the current year's return and the Non-resident Landlord Scheme paperwork get sorted together. Horizon runs landlord disclosures end to end on a fixed fee agreed upfront, with complex work from £750; book a free 30-minute clarity call and one conversation will usually tell you which route applies, how many years are in play and what the settlement will roughly look like.

Go deeper

Sources and further reading

This is general information for the 2026/27 UK tax year, not personal tax advice; speak to a Chartered Tax Adviser about your own position.

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