Legal & Tenure

Self Assessment for Landlords — What to Declare, Deadlines, and Penalties in 2026

If you receive rental income above £1,000 in a tax year you must register for Self Assessment and file a tax return with HMRC. This guide walks through registration, what to include on your return, the 31 January filing deadline, and the penalty regime for late or incorrect returns.

Published: 1 Jan 2026 · Updated: 1 Mar 2026 · 6 min read

Do You Need to Register for Self Assessment?

You must register for Self Assessment with HMRC if your gross rental income (before expenses) exceeds **£1,000 in a tax year**, or if your net rental profit means you have tax to pay. Even if you pay tax via PAYE on your employment income, rental income must be separately declared through Self Assessment.

If you are a new landlord, you should register as soon as reasonably possible and no later than **5 October following the end of the first tax year** in which you receive rental income. For income received in the 2025/26 tax year (ending 5 April 2026), the registration deadline is 5 October 2026.

How to Register

Register online at HMRC's website using your Government Gateway account. You will need your National Insurance number and details of your rental income. HMRC will then send you a Unique Taxpayer Reference (UTR) by post, which you will use for all future correspondence and filings.

What to Declare on Your Return

Landlords complete the **SA105 supplementary pages** (UK Property) as part of the main SA100 Self Assessment return. You will need to declare:

**Total rental income received** — gross rents from all UK property.
**Allowable expenses** — broken down by category (repairs, insurance, agent fees, and so on).
**Finance costs** — mortgage interest and other financing costs, which now generate a 20% basic rate tax credit rather than a direct deduction.
**Replacement of domestic items relief** — if applicable.
**Net rental profit or loss** — after allowable deductions.

If you have more than one rental property, you combine all income and expenses across the portfolio into a single UK property income figure (with limited exceptions for Furnished Holiday Lettings, which operated under a separate regime that was abolished from April 2025).

Key Deadlines

Milestone	Deadline
Register for Self Assessment (new landlords)	5 October after the tax year ends
Paper tax return submission	31 October
Online tax return submission	31 January
Payment of tax owed (balancing payment)	31 January
Payments on Account (if applicable)	31 January and 31 July

The **31 January online deadline** is the one most landlords need to remember. For the 2025/26 tax year, the online filing and payment deadline is **31 January 2027**.

Payments on Account

If your Self Assessment tax bill is over £1,000 (and less than 80% of your total tax was collected via PAYE), HMRC will require you to make **payments on account** — advance instalments toward the following year's expected liability. These are each 50% of the previous year's bill, due on 31 January and 31 July.

Penalties for Late Filing and Payment

HMRC operates a structured penalty regime:

**Day 1 after deadline:** Automatic £100 fixed penalty (applies even if no tax is owed).
**3 months late:** £10 per day for up to 90 days (maximum £900).
**6 months late:** 5% of the tax owed or £300, whichever is greater.
**12 months late:** A further 5% of the tax owed or £300.

Late payment also incurs interest and surcharges. The penalties accumulate rapidly — filing on time is almost always cheaper than the cost of delay.

Using a Calculator Before You File

Knowing your estimated liability before the filing deadline lets you plan your cash flow and avoid underpayment surprises. Use our [rental income tax calculator](/rental-income-tax-calculator) to estimate what you will owe on your 2025/26 rental profits.