How to File a Self-Assessment as a Landlord

# How to File a Self-Assessment as a Landlord

If you have rental income above the £1,000 property allowance, you must declare it via self-assessment. The process is straightforward once you know the structure.

Step 1 — Register

If this is your first year of rental income:

• Register at gov.uk/register-for-self-assessment.
• Deadline: 5 October after the end of the tax year (e.g. for 2025/26 tax year, register by 5 October 2026).
• HMRC sends a Unique Taxpayer Reference (UTR) by post within 10 working days.
• Then enrol for online services and wait for the activation code (another 7 days).

Start early — leaving registration to January is the most common penalty trigger.

Step 2 — Gather your records

For the tax year (6 April–5 April):

• All rental income received (date, amount, property).
• Bank statements for the rental account.
• Invoices and receipts for allowable expenses.
• Mortgage interest statements (annual).
• Insurance, agent fees, ground rent statements.
• Mileage log for property visits.
• Previous year''s return for comparison.

Step 3 — Complete SA100 + SA105

You file the main SA100 plus the SA105 UK Property supplementary pages.

Key SA105 boxes:

• Box 5 — total rents and other income.
• Box 24 — rent, rates, insurance, ground rent.
• Box 25 — property repairs and maintenance.
• Box 27 — legal, management and other professional fees.
• Box 29 — other allowable property expenses.
• Box 41 — residential property finance costs (the 20% credit boxes 44–45).
• Box 36 — adjusted profit.
• Box 39 — taxable profit for the year.

If you have multiple properties, you sum income and expenses across all of them on one SA105 (UK Residential).

Step 4 — Apply Section 24 correctly

Mortgage interest no longer comes off rental income directly. Instead:

1. Calculate rental profit ignoring mortgage interest.
2. Calculate tax on total income.
3. Subtract a tax credit equal to 20% × the lower of: finance costs, property profits, or adjusted total income above the personal allowance.

The online HMRC form does this calculation automatically when you enter the correct boxes — but check the result against your own working.

Step 5 — Pay

• Balancing payment for the tax year — due 31 January.
• First payment on account for the following year — also due 31 January (50% of last year''s bill).
• Second payment on account — due 31 July (the other 50%).

Payments on account apply if your previous tax bill was over £1,000 and less than 80% was deducted at source.

Deadlines summary

Penalties

• £100 automatic late filing (one day late).
• £10/day after 3 months (max £900).
• 5% of tax due after 6 months (min £300).
• 5% of tax due after 12 months.
• Late payment: 5% of unpaid tax after 30 days, 6 months, 12 months.
• Interest accrues from the due date.

Making Tax Digital (MTD) — April 2026

From April 2026, landlords with property income over £50,000 must:

• Keep digital records (cloud accounting).
• Submit quarterly updates to HMRC.
• Final declaration each year.

From April 2027 the threshold drops to £30,000. Plan now: pick accounting software (FreeAgent, Hammock, Landlord Studio, Xero) and get records flowing through it.

Common mistakes

• Missing the 5 October registration deadline.
• Treating mortgage capital as deductible (only interest qualifies for the 20% credit).
• Claiming improvements as repairs (capital, not revenue).
• Forgetting payments on account.
• Not keeping receipts (HMRC requires 5+ years).
• Filing the SA100 without the SA105.
• Mixing rental and personal expenses in one bank account.

When to use an accountant

• Multiple properties.
• Limited company structure.
• Mixed-use property.
• Capital gains in the year.
• First year of letting.
• Foreign property income.
• Partnership or joint ownership.

Property-specialist accountants typically charge £300–£600 per return; usually pays for itself in correct expense capture.

Bottom line

Register early, keep records as you go, file by 31 January, and pay on time. For income above £50,000 from April 2026, MTD makes cloud accounting essential. Penalties are easy to avoid and expensive to ignore.