Rental Income Disclosure Deadlines: The 90-Day Let Property Campaign Rule (2026)
Last updated 24 June 2026 · 9 min read · By the LandlordTaxAi Editorial Team
The short answer
If you have undeclared rental income, you can use HMRC’s Let Property Campaign to put it right. Once you notify HMRC and get an acknowledgement, you have 90 days to calculate and pay what you owe. Coming forward voluntarily means much lower penalties than if HMRC catches you first.
Thousands of UK landlords have rental income they never declared — an inherited flat, a room let out, a property kept on after moving in with a partner. HMRC knows. It cross-references Land Registry, letting agents, deposit schemes and tenancy data, and it runs a permanent disclosure route called the Let Property Campaign for exactly this situation.
The campaign is genuinely a good deal: come forward voluntarily and you get the lowest penalties and certainty over your position. Ignore it and wait to be caught, and you face far higher penalties — or, for deliberate evasion, criminal prosecution.
The one number that trips people up is the 90-day deadline. This guide explains every disclosure deadline, how far back HMRC can go, and what the penalties actually are. If you’re not sure whether you even need to declare, start with do I need to declare rental income?.
Free calculator · no sign-up
Undeclared Rental Profit & Tax Estimator
Estimate the rental profit and tax for each undeclared year before you notify HMRC and start the 90-day clock.
Result
- Taxable profit (rent − expenses)
- £11,200
- Income Tax at 40%
- £4,480
- Less mortgage interest credit (20%)
- − £1,000
- Tax due on this property
- £3,480
- Income after tax
- £7,720
Estimate only — add late-payment interest and a behaviour-based penalty for your full disclosure figure.
The two deadlines that matter
The Let Property Campaign is a two-step process, and each step has its own deadline. Miss the second one and you lose the protection of the campaign’s terms entirely.
First you notify HMRC that you intend to disclose. HMRC sends an acknowledgement with a Disclosure Reference Number. From the date of that acknowledgement, your 90-day clock starts.
| Step | What you do | Deadline |
|---|---|---|
| 1. Notify | Tell HMRC you want to disclose undeclared rental income | Any time — this starts the process |
| 2. Disclose & pay | Work out the tax, interest and penalty, submit and pay | Within 90 days of HMRC’s acknowledgement |
| Can’t pay in full? | Agree a payment plan (Time to Pay) | Must be arranged by the same 90-day deadline |
If you don’t pay (or agree a payment plan) within the 90 days, you cannot complete your disclosure under the campaign and lose its favourable terms. Only notify when you’re ready to act.
How far back HMRC can go
How many years you must disclose depends on why the income went unreported. HMRC categorises behaviour, and the category sets both the look-back period and the penalty range.
This is why honesty about your own circumstances matters: a genuine mistake is treated very differently from a deliberate decision not to declare.
| Behaviour | Years to disclose | Typical penalty |
|---|---|---|
| Reasonable care taken (innocent error) | Up to 4 years | No penalty |
| Careless / failed to take reasonable care | Up to 6 years | 0%–30% of the tax |
| Deliberate | Up to 20 years | 20%–100% of the tax |
Penalties are also lower for an unprompted disclosure (you came forward before HMRC contacted you) than a prompted one. The Let Property Campaign route is treated favourably — but only if you’re upfront.
What you’ll owe: tax, interest and penalty
Your total bill has three parts. Getting an early estimate helps you plan for the 90-day payment deadline rather than being caught short.
- Tax — the income tax due on the rental profit for each undeclared year, at your band for that year
- Interest — charged on the late tax from the date it was originally due (this is never waived)
- Penalty — a percentage of the tax, set by your behaviour and whether the disclosure was prompted
Use the calculator above to estimate the rental profit and tax for each year, then add interest and a penalty percentage to gauge your 90-day target. For the profit rules, see allowable expenses for landlords.
How to make a disclosure, step by step
Going forward: declare on time and prepare for MTD
Once you’re up to date, the goal is to never need a disclosure again. That means declaring rental income each year through Self Assessment — and, from April 2026, through Making Tax Digital if your qualifying income is over £50,000.
If your disclosure pushes your record-keeping into shape, you’re already most of the way to MTD-ready. See how to register for MTD for Income Tax and the Self Assessment deadlines for 2026/27.
Get straight with HMRC — and stay straight
LandlordTaxAi reconstructs your rental income and expenses from bank statements, so a disclosure is fast and accurate — and every future year files on time, automatically.
See how it worksA worked example
Tom let a flat for 5 years without declaring £6,000 profit a year. He’s a higher-rate taxpayer and comes forward voluntarily (careless behaviour).
| Undeclared profit | £6,000 × 5 years = £30,000 |
| Tax at 40% | £12,000 |
| Interest (illustrative) | + several hundred £ per year, compounding |
| Penalty (careless, unprompted) | 0%–30% of the tax — potentially £0–£3,600 |
| Deadline to pay once notified | 90 days |
Had HMRC caught Tom first and judged it deliberate, the look-back could stretch to 20 years and the penalty up to 100% of the tax — coming forward voluntarily is dramatically cheaper.
Frequently asked questions
How long do I get to pay under the Let Property Campaign?
90 days from the date HMRC acknowledges your notification — to both calculate and pay (or arrange a payment plan).
Who can use the Let Property Campaign?
Individual landlords letting residential property in the UK or abroad. It doesn’t cover companies, trusts, or commercial-only lettings.
How many years do I have to disclose?
Up to 4 years if you took reasonable care, 6 years if careless, and up to 20 years if the failure was deliberate.
Will I get a penalty if I come forward?
Possibly, but a voluntary, unprompted disclosure attracts the lowest penalties — often 0% for innocent errors. Waiting to be caught means much higher penalties or prosecution.
What if I can’t pay the full amount in 90 days?
You must agree a Time to Pay arrangement with HMRC by the 90-day deadline. Do nothing and you lose the campaign’s protection.
Does HMRC really know about my rental?
Often, yes. HMRC matches Land Registry, letting agents, tenancy deposit schemes and other data, so undeclared lets are increasingly easy to spot.
Written and reviewed by the LandlordTaxAi Editorial Team. Our guides are reviewed against current HMRC guidance and updated when the rules change. Operated by LandlordTaxAi, United Kingdom. Follow us on LinkedIn.
Last reviewed: 24 June 2026 · Researched against primary UK sources for the 2026/27 tax year: https://www.gov.uk/government/publications/let-property-campaign-your-guide-to-making-a-disclosure/let-property-campaign-your-guide-to-making-a-disclosure; https://www.gov.uk/government/publications/hmrc-your-guide-to-making-a-disclosure/your-guide-to-making-a-disclosure; https://www.litrg.org.uk/savings-property/property-income/reporting-property-income-hmrc. This article is informational only and does not constitute tax advice. Check the latest details on GOV.UK or with a qualified accountant.