Form SA105 Landlord Tax Return
UK Form SA105 guide for property income: box-by-box filing instructions, £1,000 property allowance, Section 24 Box 44 mortgage interest credit, and joint ownership rules.
In one sentence
Form SA105 is the HMRC Self Assessment supplementary page used by UK individual landlords to report gross rental income, allowable property expenses, and Section 24 mortgage interest.
Quick answer
- Required if gross rental income exceeds £1,000 per tax year
- Box 5/6: Gross rent received before deducting letting agency fees or expenses
- Box 44: Residential mortgage interest entered here for the 20% basic rate tax credit
- Joint owners must file separate SA105 forms reflecting their percentage share
Form SA105: UK Landlord Property Income Tax Return Guide
If you receive rental income from UK residential or commercial property in your personal name, HMRC requires you to complete Form SA105 (Property) as part of your annual Self Assessment tax return (SA100).
Whether you let out a single buy-to-let, a portfolio of residential properties, or a commercial unit, understanding how to report rental receipts, allowable expenses, and residential mortgage interest on Form SA105 is vital to avoid overpaying tax.
Do you need to complete Form SA105?
You must submit Form SA105 if your total gross property income (before deducting expenses) exceeds £1,000 in a tax year:
- Gross Income Under £1,000: Covered by the UK Property Allowance. The income is tax-free and does not need to be declared on SA105 unless you wish to record a property loss.
- Gross Income Over £1,000: You must declare all property income on Form SA105 and elect to deduct either your actual allowable expenses or the £1,000 flat property allowance.
Key Boxes on Form SA105 Explained
Form SA105 separates your income and expenses into specific numbered boxes:
| Box Number | Description | Filing Guidance |
|---|---|---|
| Box 5 / 6 | Total gross rents and other property income | Enter gross rent received before deducting letting agency fees, repairs, or expenses. |
| Box 7 - 13 | Allowable landlord expenses | Enter itemized costs: ground rent, property insurance, gas safety certificates, repairs, cleaning, agency fees, and accountancy costs. |
| Box 20.1 | Property Income Allowance (£1,000) | Claim this flat deduction if your total expenses are less than £1,000 (cannot claim alongside actual expenses). |
| Box 44 | Residential finance costs (Section 24) | Enter total buy-to-let mortgage interest and loan arrangement fees here (used to calculate your 20% tax credit). |
| Box 26 / 27 | Unused property losses brought forward | Record accumulated rental losses from previous years to offset against this year's net rental profit. |
Reporting Residential Mortgage Interest (Section 24)
Under UK Section 24 tax rules, residential buy-to-let mortgage interest is not deductible as an expense in Box 12.
Instead, you enter your total mortgage interest in Box 44. HMRC calculates a 20% basic rate tax credit (tax reducer) which is deducted directly from your final Self Assessment tax bill.
Higher rate (40%) and additional rate (45%) taxpayers effectively lose half or more of their previous mortgage interest relief, which is why many landlords evaluate transferring properties into a limited company SPV.
Joint Ownership Rules on Form SA105
If a rental property is owned jointly (e.g. by a married couple or business partners):
- Each joint owner must complete their own separate Form SA105 showing their percentage share of income and expenses.
- Married couples and civil partners are taxed 50/50 by default, unless a formal Form 17 election and Deed of Beneficial Interest are submitted to HMRC.
Read our guide on allowable expenses for UK landlords or see how our specialist landlord accounting service prepares your SA105 pages and tax return.
Need help completing your SA105 property tax pages?
Book a 20-minute call with an experienced UK landlord accountant. We will review your rental accounts, calculate Section 24 mortgage tax relief, and file your SA105 return accurately.
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