Filing Self Assessment as a UK landlord involves the SA100 main return, the SA105 UK Property pages, and (if a disposal happened in the year) the SA108 Capital Gains pages. For 2025/26 the cycle ends with online filing by 31 January 2027. For 2026/27, sole-trader landlords with qualifying income above £50,000 move into MTD for ITSA, which replaces the single year-end SA return with four quarterly updates plus a Final Declaration.

This guide covers the 2025/26 SA105 walkthrough, the deadlines, the Section 24 finance-cost mechanic that catches most landlords on the form, the £1,000 property allowance choice, the joint-ownership and Form 17 rules, and the MTD transition that affects the 2026/27 cycle. It is the practical companion to our Section 24 complete guide, MTD for landlords guide, and CGT on UK property sale page.

Who Has to File: The 2025/26 Test

You must file a 2025/26 Self Assessment return if any of the following apply:

  • Gross rental receipts above £2,500 (or above £1,000 if you have other reasons to file, or if you want to claim expenses instead of using the property allowance).
  • Rental profit above the £1,000 property allowance and you are a higher- or additional-rate taxpayer.
  • You disposed of a UK residential property in 2025/26 (CGT must also be reported within 60 days of completion through the UK Property service).
  • You received rental income from overseas property (regardless of UK income).
  • You have rental losses to carry forward.
  • HMRC has issued you a notice to file.

Below £1,000 of gross rents and no other reason to file, the property allowance covers the income automatically and no return is needed. Between £1,000 and £2,500 of gross rents and no other reason to file, you may be able to settle the tax via PAYE coding without a return; ring HMRC and ask. Above £2,500 of gross rents, a return is mandatory.

Key Dates for the 2025/26 Cycle

DateAction
31 July 2026Second payment on account for 2025/26 due
5 October 2026Deadline to register for Self Assessment if first time filing
31 October 2026Paper return filing deadline (not recommended)
31 January 2027Online filing deadline AND balancing payment deadline AND first payment on account for 2026/27
31 July 2027Second payment on account for 2026/27

The 31 January deadline is the immovable one. The official HMRC reference is gov.uk/self-assessment-tax-returns/deadlines. Late filing penalties under FA 2009 Sch 55 start at £100 fixed (even if no tax is due), escalate to £10 a day after three months for up to 90 days, then 5% or £300 after six months, then another 5% or £300 after twelve months.

Documents to Gather Before You Start

  • Rental income: agent statements, bank statements showing rent received, any direct-paid rent records, retained deposits forfeited to you, premiums received from tenants on lease grants.
  • Finance costs: annual mortgage interest certificates from each lender, broker fee invoices, arrangement fee invoices (often deductible as finance costs subject to Section 24).
  • Allowable expenses: agent commission, repairs invoices, insurance documents, gas safety / EICR / EPC certificates, ground rent and service charge demands, accountancy fees, advertising costs, replacement-of-domestic-items receipts.
  • Capital improvements (kept for CGT, not deducted against rent): kitchen replacements, bathroom replacements, extensions, structural works.
  • Disposal records (if applicable): sale completion statement, original purchase costs, legal and stamp duty costs on acquisition, capital improvement costs, costs of disposal.
  • Joint ownership documents: declaration of trust, Form 17 (if filed), evidence of beneficial ownership shares.

SA105 UK Property Walkthrough

SA105 is the property income section attached to the SA100 main return. Box numbers shift slightly year to year, so the names below match the 2024-25 form which is the most recently published version at the time of writing.

Section A: Property details

Number of properties let (include each separately let unit). Whether furnished or unfurnished. Whether the income is reported on cash basis or accruals basis (cash basis is the default for landlords with gross rents up to £150,000; accruals basis can be elected). Whether you are reporting under the property allowance.

Section B: Property income

Gross rents received from all UK properties combined (one figure for the whole portfolio, not per property). Include rent paid by tenants and any service charges recharged to tenants. Include any forfeited deposits and any reverse premiums received. Do not include income from a lodger in your main home where you have elected for Rent a Room treatment (that goes elsewhere on the return).

Section C: Allowable expenses

Each major expense category has its own box. The main categories:

  • Rents paid, rates, insurance, ground rents: insurance premiums, ground rent paid to freeholder, residential service charges paid, rates (water rates, council tax where landlord pays).
  • Property repairs and maintenance: repairs to restore the property to its original state (not improvements). Like-for-like roof tile replacement, broken boiler repair, redecoration, replacement of a damaged front door with one of equivalent specification.
  • Non-residential property finance costs: finance costs on commercial property only. Residential property finance costs go in the separate Section 24 box below.
  • Legal, management and other professional fees: letting agent commission, accountancy fees, legal fees for tenancy disputes, management fees. NOT property purchase legal fees (capital).
  • Costs of services provided, including wages: wages for any employed property managers, cleaners, gardeners.
  • Other allowable property expenses: advertising, travel costs to and from properties for management, mileage at HMRC approved rates, telephone, postage, stationery.

Section D: The Section 24 finance cost box

This is where most landlord errors happen. Box 44 on the 2024-25 form (named "Residential finance costs not included in 'Loan interest and other financial costs'"). Enter the full amount of mortgage interest and other residential finance costs paid in the year. HMRC's automatic calculation will:

  1. Add this figure to taxable rental profit (so it is not a deduction against rents).
  2. Apply a 20% basic-rate tax credit against your overall income tax liability.
  3. Cap the credit at the lower of: the finance costs, your property profits for the year, or your adjusted total income above the personal allowance.
  4. Carry forward any unrelieved excess to future years' finance cost relief.

Common mistakes: entering interest in the "loan interest and other financial costs" box (which would attempt a full deduction and be wrong), splitting interest between Section 24 box and main expenses (double-counting), or forgetting to include broker fees and arrangement fees which are also finance costs.

Section E: Other property income / loss reliefs

If your property business made a loss for the year, the loss is automatically carried forward to set against future UK property profits. No election is needed. Losses from one property automatically offset profits from another in the same year.

The £1,000 Property Allowance Choice

If gross rental receipts are above £1,000, you choose between two methods:

  • Method A (property allowance): deduct £1,000 from gross rents, pay tax on the rest, no other expenses allowed.
  • Method B (actual expenses): claim all actual allowable expenses, no £1,000 allowance.

Pick whichever produces the lower taxable figure. Method A wins when total expenses (excluding finance costs, which sit separately under Section 24) are less than £1,000. Method B wins everywhere else, which is almost always.

The property allowance cannot be combined with Rent a Room relief on the same income, and cannot be claimed against income from a property you let to your employer (or a close company you control).

Joint Ownership and the Form 17 Election

Property held jointly by spouses or civil partners has a default 50/50 income split for tax (ITA 2007 s.836), regardless of actual beneficial ownership. To override the default with the actual beneficial split (typically to push more rental profit to the lower-earning spouse), you need:

  1. A declaration of trust establishing the actual beneficial ownership (e.g. 99/1 in favour of the lower-earning spouse).
  2. Form 17 filed with HMRC within 60 days of signing, declaring the income split exactly matches the beneficial split.

The election only takes effect from the date the Form 17 is filed (not from the start of the tax year). HMRC will not accept an arbitrary income split that does not match beneficial ownership.

For unmarried co-owners and joint-tenants other than spouses, the income split follows the beneficial ownership directly without need for a Form 17 election.

Online Filing: The HMRC Portal Step by Step

  1. Sign in at gov.uk/log-in-file-self-assessment-tax-return with your Government Gateway credentials. First-time filers register for SA using their UTR.
  2. Select "Tax return" for the 2025-26 tax year. Confirm your personal details.
  3. Tailor the return: tick "UK property income" to add the SA105 pages. Tick "Capital Gains" if you sold a property. Tick employment, pensions, dividends as applicable.
  4. Work through the SA105 pages section by section using the documents gathered above. The system auto-saves at each step.
  5. Review the calculation summary. Cross-check the residential finance cost figure and the property profit figure against your records.
  6. Submit electronically. Note the submission receipt number and download the PDF copy of the filed return.
  7. Pay any balancing tax due by 31 January 2027 (online banking using your UTR as the reference is fastest). Set up payments on account direct debits if applicable.

The MTD Transition for the 2026/27 Cycle

MTD for ITSA went live on 6 April 2026. The threshold for sole-trader landlords is £50,000 of qualifying income (gross trading plus gross property receipts). Threshold drops to £30,000 from 6 April 2027 and £20,000 from 6 April 2028. The official sign-up checker is at gov.uk/guidance/check-when-to-sign-up-for-making-tax-digital-for-income-tax.

What changes for landlords above the threshold from 6 April 2026:

  • Quarterly digital updates due 7 August (Q1), 7 November (Q2), 7 February (Q3), 7 May (Q4).
  • Final Declaration due 31 January following the tax year (so 31 January 2028 for the 2026/27 year).
  • The Final Declaration replaces the year-end SA105/SA100 process for the rental business.
  • MTD-compatible software is mandatory. Spreadsheets must be MTD-bridged.

Limited companies are outside MTD for ITSA entirely and continue to file annual CT600 returns.

Payments on Account

If your 2024/25 tax liability exceeded £1,000 and was less than 80% covered by tax at source (PAYE on employment income), you will have payments on account for 2025/26. Each payment is half the previous year's liability:

  • First payment on account: 31 January 2026 (already paid)
  • Second payment on account: 31 July 2026
  • Balancing payment: 31 January 2027 (settles the actual 2025/26 liability)
  • First payment on account for 2026/27: 31 January 2027 (same date)

Payments on account can be reduced where you expect the current-year liability to be lower than the previous year's. The election is made via Form SA303 or on the online return. Reductions that turn out to be wrong attract interest on the underpayment, so reduce only with reasonable grounds.

The 60-Day CGT Reporting on Property Disposals

If you sold a UK residential property in 2025/26 (or sell one in 2026/27), the CGT must be reported and paid within 60 days of completion through the UK Property CGT service. This is separate from the Self Assessment cycle. The disposal must also be entered on the SA108 Capital Gains pages of the year-end return, with the 60-day payment shown as tax already paid. Missing the 60-day deadline triggers Schedule 55 FA 2009 penalties from £100, rising to £300 after six months.

CGT rates on residential property for 2025/26 are 18% (basic-rate band remaining) and 24% (higher-rate band), unchanged from 30 October 2024 when the Autumn 2024 Budget cut the higher rate from 28%. The annual exempt amount is £3,000.

Common Mistakes and How to Avoid Them

  • Entering mortgage interest in the wrong box. Residential finance costs go in the dedicated Section 24 box, not in "Loan interest and other financial costs".
  • Claiming capital improvements as repairs. A new kitchen is capital. Replacing a few broken cupboard doors is a repair. The boundary is in HMRC's PIM2020 and case law.
  • Forgetting replacement-of-domestic-items relief. Like-for-like replacement of furniture, white goods, and soft furnishings in furnished lets is deductible in the year of replacement (ITTOIA 2005 s.311A).
  • Wrong joint-ownership split. Default is 50/50 for spouses regardless of beneficial ownership. To override, file Form 17 with a declaration of trust.
  • Missing the 60-day CGT reporting window. The Self Assessment SA108 page does not satisfy the 60-day rule for residential disposals.
  • Treating mortgage capital repayments as a deduction. Only the interest element is a finance cost; the capital element is not deductible at all.
  • Not registering for Self Assessment within the 5 October deadline. First-time landlord filers must register by 5 October following the end of the first tax year of rental.

When to Use a Specialist

DIY filing makes sense for a single property with simple income and standard expenses. Use a specialist if any of the following apply:

  • Portfolio of three or more properties.
  • Any disposal in the year (the 60-day CGT computation alone often pays for the year's fee).
  • Joint ownership where a Form 17 election is or could be in play.
  • First year above the MTD for ITSA threshold.
  • Mixed sole-trader and limited-company structure.
  • HMRC enquiry or compliance check open or recently closed.

The official HMRC SA105 notes are at gov.uk/government/publications/self-assessment-uk-property-sa105.