Could HMRC Find Your Undeclared Rental Income

Felix & Co HMRC Free Let Property Campaign Guide

COULD HMRC FIND YOUR UNDECLARED RENTAL INCOME? What Every Landlord Should Know Before HMRC Asks the Question First

Could HMRC Find Your Undeclared Rental Income?

If you haven’t told HMRC about some, or all, of your rental income, it is worth asking a harder question: how would HMRC actually find out? This free guide from Felix & Co Chartered Accountants explains where HMRC gets its information, the mistakes that quietly turn ordinary landlords into disclosure cases, and what to do before HMRC raises the question for you.

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How HMRC Actually Finds Undeclared Rental Income

It is a common assumption: if a landlord hasn’t told HMRC about their rental income, HMRC has no way of knowing. In reality, HMRC has access to an increasing range of data sources, and uses automated systems to cross-check them against the Self Assessment returns it already holds.

  • Land Registry records showing who owns which property
  • Letting agent data and information from property listing platforms
  • Bank and financial institution information
  • Information shared by overseas tax authorities under international agreements
  • Mortgage and other property-related data
  • Information from third parties, including tenants and other landlords

A property that appears to generate rental income, with no matching income declared, is exactly the kind of mismatch these systems are designed to flag.

“If HMRC hasn’t contacted me yet, does that mean there’s no problem?”

Not necessarily. The absence of contact from HMRC does not mean rental income has been correctly reported, or that HMRC cannot investigate in the future. A disclosure made voluntarily, before HMRC identifies the issue, generally puts a landlord in a stronger position than waiting to be approached.

Six Ways Landlords Quietly Become Non-Compliant

This guide walks through the six areas we see most often among landlords considering a Let Property Campaign disclosure:

  • Common reasons landlords become non-compliant — the accidental landlord, the inherited property, and the “my agent handles it” assumption
  • Overseas landlord issues — misunderstandings about non-resident status and the Non-Resident Landlord Scheme
  • Incorrect expense claims — mortgage payments claimed in full, and repairs confused with capital improvements
  • Missing rental income — properties never registered, income declared for some years but not others, and cash rent left out entirely
  • Property ownership changes — joint ownership, changing ownership splits, and income reported on the wrong return
  • Section 24 and mortgage interest mistakes — the 2017 rule change that continues to catch out higher and additional rate taxpayers

The Small-Amount Trap

A property generating a modest amount of monthly rent can feel too small to bother declaring. Over several years, however, even a modest sum adds up to a significant figure once HMRC’s review period is taken into account.

£800 a month

Adds up to £9,600 a year in rental income — before any expenses are even considered.

Over six years

The same figure becomes £57,600 — a very different number to explain to HMRC after the fact.

Section 24: Why Your Tax Bill May Have Risen Even Though Your Rent Hasn’t

The rules restricting mortgage interest relief for individual landlords, often referred to as “Section 24”, are one of the most misunderstood areas of residential property tax. For most individual landlords, finance costs can no longer be deducted directly from rental income. Instead, relief is given as a basic-rate tax reduction, applied after tax on rental profit has already been calculated.

For higher and additional rate taxpayers in particular, this can mean paying more tax overall than expected, even where nothing else about the property has changed — and it is a frequent source of undetected errors in landlords’ existing tax returns.

How Felix & Co Can Help

Felix & Co is a UK accountancy practice led by a Chartered Certified Accountant, working with landlords to review rental income, identify where reporting may have gone wrong, and prepare accurate, well-supported disclosures where needed. We handle the calculations, the paperwork and the correspondence with HMRC, so you can resolve the position with confidence rather than uncertainty.

Frequently Asked Questions

How does HMRC actually find out about undeclared rental income?

Through data matching across sources including the Land Registry, letting agents, banks, mortgage lenders and information shared by overseas tax authorities, cross-checked automatically against the tax returns HMRC already holds.

My letting agent already deducts tax from my rent — doesn’t that mean I’m compliant?

Not necessarily. Tax deducted under the Non-Resident Landlord Scheme is generally a payment on account, not a final settlement. A Self Assessment return is normally still required to establish the correct final position.

I’ve lost my records — can I still make a disclosure?

Yes. This is a common situation. Information can often be reconstructed from bank statements, letting agent records, mortgage statements and previous tax returns.

Why has my tax bill gone up when my rent hasn’t changed?

This is often the effect of the Section 24 mortgage interest restriction, which changes how rental profit is taxed for individual landlords, particularly higher and additional rate taxpayers.

We changed our property ownership split years ago — could that affect our tax returns?

Possibly. The correct tax treatment depends on the legal and beneficial ownership position, and on whether the required elections or notifications were made to HMRC at the time.

Is this guide free to download?

Yes, with no obligation to use Felix & Co’s services afterwards.

Not sure where you stand? Complete the short form above to get your free copy of “Could HMRC Find Your Undeclared Rental Income?” by email instantly.

Felix & Co Chartered Accountants · Belix House, 19 Raymill Road East, Maidenhead, SL6 8SW · 01895 348 097 · accounts@felixaccountants.com