Self Assessment

Self Assessment is HMRC's system for collecting income tax on earnings that are not taxed at source through Pay As You Earn (PAYE). For landlords, it is the mechanism by which rental profits, gross rent received, minus allowable expenses, are declared to HMRC and assessed for income tax each tax year. Most individual private landlords letting residential property in the private rented sector must register for Self Assessment, file an annual tax return, and pay any tax due by HMRC's prescribed deadlines.

Who needs to file

Not every landlord must file a Self Assessment return. The requirement depends on the level of income:

• Property income allowance - if your total gross rental income is £1,000 or below in a tax year, you do not need to notify HMRC or file a return, as the income is covered by the property income allowance introduced in 2017.

• Between £1,000 and £2,500 gross - HMRC may be able to collect tax owed through an adjustment to a PAYE code rather than a return. Contact HMRC to confirm.

• £2,500 or more in net rental profits after expenses - you must file a Self Assessment return.

• £10,000 or more in gross rental income before expenses - you must file a Self Assessment return regardless of the level of expenses.

Landlords operating through a limited company do not file a Self Assessment return for their property income; the company files a Corporation Tax return instead. Self Assessment applies to individual unincorporated landlords only.

Key deadlines

Each tax year runs from 6 April to the following 5 April. The main Self Assessment deadlines are:

• 5 October - register with HMRC for Self Assessment by this date in the tax year following the one in which you first received rental income. For example, if your first rental income was received during the 2025/26 tax year, you must register by 5 October 2026.

• 31 January - file your online Self Assessment return and pay any tax owed for the previous tax year. This is also the deadline for the first payment on account towards the current year's tax bill.

• 31 July - pay the second payment on account.

• Payments on account - if your Self Assessment tax bill is more than £1,000 and less than 80% of your total tax is collected at source, HMRC requires you to make two advance payments on account of the following year's bill.

Late filing carries an automatic £100 penalty, with further penalties accruing at three months, six months, and twelve months. Late payment triggers interest on the outstanding amount.

Which forms do landlords use?

Landlords filing a paper return must complete form SA100 (the main Self Assessment tax return) and the SA105 supplementary pages for UK property income. The SA105 covers total rents received, allowable expenses, and the mortgage interest figure used to calculate the Section 24 finance cost tax credit. Online filing uses a dynamic form that adds the relevant sections automatically. The SA105 is published annually by HMRC and updated for each tax year; always use the version for the relevant year.

Allowable expenses

Landlords pay income tax on rental profits, not gross rental income. Allowable expenses are costs incurred wholly and exclusively for the purpose of the rental business that can be deducted from gross rent to arrive at the taxable profit. Common allowable expenses include letting agent fees, property insurance, repairs and maintenance (but not improvements), accountancy fees, ground rent and service charge, and certain utility costs during void periods. Interest on a buy-to-let mortgage is not deductible as an expense but qualifies for a 20% tax credit under the Section 24 rules that have applied since April 2020.

Capital expenditure, money spent on improvements, extensions, or items that increase the value of the property, is not allowable as a revenue expense and is treated differently for Capital Gains Tax purposes when the property is eventually sold.

For a detailed breakdown of what landlords can and cannot claim, see the August guide to allowable expenses. August's expenses tracking  categorises every transaction against HMRC's allowable expense categories in real time, so the income and expenditure summary for your Self Assessment return is ready throughout the year rather than assembled in January.

How to register

Landlords who are required to file must register with HMRC by 5 October following their first tax year of rental income. Registration is completed online using form SA1 (or the SA4 for partnerships). HMRC will then issue a Unique Taxpayer Reference (UTR), the ten-digit number used on every subsequent tax return and correspondence. For a step-by-step walkthrough of registering with HMRC, obtaining your UTR number, and what to expect after registration, see the August guide to registering with HMRC as a landlord.

Self Assessment and Making Tax Digital

Self Assessment is being replaced, in stages, by Making Tax Digital for Income Tax (MTD for IT) for landlords above certain income thresholds. From 6 April 2026, landlords whose combined gross property and self-employment income exceeded £50,000 in the 2024/25 tax year must use MTD-compatible software to keep digital records and submit quarterly updates to HMRC, with a Final Declaration replacing the annual return at year end. The threshold drops to £30,000 from April 2027 and £20,000 from April 2028.

Landlords below these thresholds continue to file Self Assessment returns as before. MTD does not change how tax is calculated; it changes the frequency and format of reporting. For the full picture of quarterly deadlines, compatible software, and how to prepare for the transition, see the August guide to Making Tax Digital for landlords.

Record-keeping

Accurate records are the foundation of a correct Self Assessment return and the best defence if HMRC enquires into a return. Landlords should retain records of all rental income received (dates, amounts, tenancies), all expense receipts and invoices, bank statements covering the rental account, mortgage statements showing the annual interest figure, and any correspondence about the property that has a financial bearing. HMRC requires records to be kept for at least five years after the 31 January filing deadline for the relevant tax year. For an overview of the full record-keeping picture that underpins your filing, see the August entry on landlord accounting.

Statutory context

Self Assessment for individuals was introduced in the Finance Act 1994 and came into operation for the 1996/97 tax year. The legislative basis for income tax on rental income is Part 3 of the Income Tax (Trading and Other Income) Act 2005. The SA105 UK property supplementary pages are published annually by HMRC at gov.uk/government/publications/self-assessment-uk-property-sa105. The HMRC landing page for Self Assessment is at gov.uk/self-assessment-tax-returns.

Frequently asked questions

What happens if I miss the Self Assessment deadline? 

HMRC issues an automatic £100 fixed penalty the day a return is late, even if no tax is owed. A further £10 per day penalty applies from three months late, up to a maximum of £900. At six months late, the penalty increases to the higher of £300 or 5% of the tax due. At twelve months, a further 5% applies. Penalties are separate from interest charged on any unpaid tax. The full penalty schedule is set out on gov.uk.

Do I still need to file a Self Assessment return if I am enrolled in Making Tax Digital? 

For landlords in scope for MTD for Income Tax, the annual Self Assessment return is replaced by a Final Declaration, submitted using MTD-compatible software after the end of the tax year. The Final Declaration serves the same purpose as the Self Assessment return — it confirms your total income, expenses, and tax position for the year — but is submitted through software rather than the HMRC Self Assessment portal. Landlords below the MTD income thresholds continue to file a conventional Self Assessment return.

Can landlords file Self Assessment on paper? 

Yes, for now. Paper returns use form SA100 plus SA105 and must be submitted by 31 October (not 31 January, which applies to online submissions only). However, once a landlord is mandated into Making Tax Digital, digital submission is compulsory and paper filing is no longer an option.

All references reflect HMRC rules and the Making Tax Digital timetable as published as of May 2026. Tax rules can change; always verify current thresholds and deadlines on gov.uk or with a qualified tax adviser. This definition does not constitute tax advice.