Notes
Do I need to do a self assessment for rental income in the UK?
Yes, you must do a self assessment tax return if you have rental income, with one exception: if your total rental profit falls below the property allowance threshold, you do not need to report it or register. If you earn above the threshold, you must declare all rental income and can deduct expenses such as letting agent fees, repairs and insurance. Mortgage interest is not a deductible expense.
Instead, you receive tax relief at the basic rate only, regardless of your actual tax band. This is the rule that catches most landlords out. The deadline to register is 5 October in the tax year you start receiving rent.
The short version:
- You must register for self assessment if your rental profit exceeds the property allowance threshold
- Rental income includes all money received, even if your expenses exceed it
- Mortgage interest relief is restricted to basic rate only, regardless of your tax band
- Register by 5 October in the tax year you start renting
- The allowance applies to total rental profit across all properties combined, not each separately
Who must register?
You must register if your rental profit exceeds the property allowance threshold, regardless of whether you have other income or are already registered for another reason.
If your profit falls below the threshold, you are not required to register. You can choose to register and claim expenses, which may produce a refund if expenses exceed income.
The threshold applies to your total rental profit across all properties combined, not to each property individually.
What counts as rental income?
Rental income is every payment you receive for letting a property: rent, fees for parking or storage, and any deposit you keep.
You declare income in the tax year it is received, even if a tenant has not yet paid. If a tenant leaves without paying, you can claim bad debt relief after reasonable attempts to collect.
Furnished holiday lettings follow different rules and may offer different tax advantages. Check whether your property qualifies with HMRC.
Expenses and the property allowance
Deductible expenses include letting agent fees, repairs, insurance, council tax (if you pay it), utilities and advertising. Capital expenditure, such as a new boiler, is not deductible in the year of purchase. It may qualify for capital allowances over time, or be offset against the gain when you sell.
If your total rental profit falls below the property allowance, you owe no tax on rental income and do not need to register.
Section 24 and mortgage interest relief
You cannot deduct mortgage interest as a normal expense. Instead, you receive a tax credit at the basic rate of income tax only, claimed via your self assessment return.
This applies even if you are a higher-rate taxpayer. The gap between the relief you receive and what you actually paid in interest is a permanent loss, not a timing difference.
Many landlords find they owe more tax than expected because their accounting profit looks low while their taxable income remains high.
| Taxpayer type | How relief is claimed | Your position |
|---|---|---|
| Basic-rate | Full basic-rate tax relief via self assessment | Relief matches your marginal rate |
| Higher-rate | Basic-rate relief only (even if you pay tax at 40%) | You lose relief on the difference between 40% and basic rate |
| Additional-rate | Basic-rate relief only (even if you pay tax at 45%) | Significant shortfall in relief |
When to register and what happens next
Register by 5 October in the tax year you start receiving rental income. Missing this deadline may result in a penalty, but registering late is always better than not registering at all.
Once registered, you must file a return every tax year you have rental income, even if it falls below the allowance. File and pay any tax owed by 31 January after the end of the tax year. Late payment attracts interest and penalties.
The Section 24 trap: why your tax bill is not what you expect
Most guides state that mortgage interest is restricted but do not show what this means in practice. If you are a higher-rate taxpayer, you receive tax relief at basic rate only. The difference between that and relief at your marginal rate is a permanent loss. Many landlords discover this only when they file their first return and find they owe far more than expected, despite expenses exceeding income on paper.
This is not a penalty or an error: it is how the system works. The Section 24 tax credit is calculated at basic rate only, regardless of your tax band. Understanding this before you register lets you plan for the liability rather than be surprised by it.
When to get professional help
If you own one property with straightforward expenses, self assessment is manageable online. If you have multiple properties, significant capital expenditure, furnished holiday lettings, or you are a higher-rate taxpayer needing to plan around Section 24, an accountant will save you money and avoid costly errors.
If your profit is below the threshold and you choose not to register, no professional help is needed unless you later decide to claim expenses.
Common questions
Can I claim all my mortgage interest as an expense?
No. Mortgage interest is not a deductible expense. You receive tax relief at the basic rate only, regardless of your actual tax band, claimed as a tax credit in your self assessment return.
What if my rental expenses exceed my rental income?
You have a loss. You must still declare it if you are registered. You can carry it forward to offset rental profits in future years, or in some cases claim relief against other income.
Do I need to register if I own a property jointly?
Yes, but each co-owner registers separately and reports their own share of income and expenses. Your share depends on how the property is owned.
What happens if I do not register when I should?
HMRC can issue a penalty. The size depends on how late you register and whether the delay was deliberate. Registering late is always better than not registering.
Can I claim losses from before I registered?
No. You can only claim losses from the tax year you registered onwards. Earlier losses are not available.
The complete system
the Claro guide
For the full step-by-step process, the Claro guide is the complete system to act on this.