Self Assessment for Landlords: Your January Checklist

Every January, the same thing happens. Landlords who have meant to "sort the paperwork" since the summer find themselves on the evening of the 30th, hunting for a boiler invoice from last March. I have been doing this for thirty-six years, and I am not an accountant, but I have seen what makes a landlord's tax return calm and what makes it painful. The difference is almost always preparation.

This checklist is for landlords who own property in their own name. If you own through a company, the rules are different and your accountant will guide you.

The dates that matter

For the 2025-26 tax year (6 April 2025 to 5 April 2026), GOV.UK sets out:

• 31 October 2026: deadline for a paper return.
• 30 December 2026: deadline to file online if you want any tax you owe collected through your PAYE tax code, where that is available to you.
• 31 January 2027: deadline for your online return, and to pay the tax you owe.
• 31 July 2027: the second payment on account, if you make them.

If you started letting during 2025-26 and have never filed a return, you should have told HMRC by 5 October 2026. If you have missed that, register now rather than waiting.

Late filing is expensive. Miss the 31 January deadline and there is an initial £100 penalty, even if you owe no tax. After three months, daily penalties of £10 a day can follow, up to £900. Further penalties apply at six and twelve months. Late payment brings its own penalties and interest.

Payments on account: the January surprise

Many landlords are caught out the first time they owe tax through self assessment. As well as paying the balance for last year, you may have to make a payment on account towards the current year. Each payment is half of last year's tax bill, due on 31 January and 31 July.

You do not need to make payments on account if last year's bill was less than £1,000, or if more than 80% of your tax was already paid at source, through PAYE for example. If you expect your income to fall, you can ask HMRC to reduce them, but if you reduce them too far you will pay interest on the shortfall.

What you can usually claim

GOV.UK lists the kinds of expenses you can deduct from rental income. They include:

• general maintenance and repairs;
• letting agent and management fees;
• landlord insurance;
• ground rent and service charges;
• utilities and council tax you pay for the property;
• services you pay for, such as cleaning or gardening;
• accountant's fees;
• legal fees for lets of a year or less, or for renewing a lease of less than 50 years;
• phone calls, stationery and advertising for the letting business;
• the business share of vehicle running costs.

Replacing furnishings. If you replace a domestic item such as a sofa, fridge, carpet or bed, you can usually claim the cost of the like-for-like replacement under replacement of domestic items relief. You cannot claim for the first purchase of an item, only its replacement.

The property allowance. If your rental income is small, you may be able to use the £1,000 property allowance instead of claiming expenses. You cannot do both, so it is only worth it if your expenses are lower than £1,000.

What you cannot claim

• Improvements. Repairs restore what was there; improvements make the property better. Replacing old windows with modern double glazing can still count as a repair, because GOV.UK treats the improvement as incidental to the repair. Adding an extension does not. Capital costs may be relevant when you sell, so keep the paperwork.
• The capital part of your mortgage. Only finance costs, such as interest, count, and those are treated differently, as below.
• Personal spending, or any part of a cost that is not for the letting.

Mortgage interest: how relief really works

This is the area I see misunderstood most often. Since April 2020, landlords who own residential property in their own name cannot deduct mortgage interest and other finance costs from rental income as an expense. Instead, relief is given as a tax reduction at the basic rate, 20%. People often call this "Section 24", after the section of the Finance Act that introduced it.

In practice, that means your rental profit is worked out before mortgage interest, taxed at your normal rates, and then 20% of your finance costs is taken off the tax bill. Higher-rate taxpayers feel the difference most, and the change can push some landlords into a higher band.

Looking ahead, the government has announced that from 2027-28 property income will have its own tax rates and the finance costs credit will move to 22%. That does not affect the return you file in January 2027, but it is worth planning for with your accountant.

Where Making Tax Digital fits

From 6 April 2026, landlords and sole traders with qualifying income over £50,000 in 2024-25 had to start using Making Tax Digital for Income Tax. The threshold falls to £30,000 from April 2027 and £20,000 from April 2028. Qualifying income is gross rent and self-employed turnover before expenses, not profit.

Importantly, GOV.UK says you still need to submit a self assessment return for the tax year before you start using Making Tax Digital. So even if you joined in April 2026, your 2025-26 return is still due on 31 January 2027 in the usual way.

The January checklist

1. Collect your rent records for 6 April 2025 to 5 April 2026. If an agent manages the property, ask for the annual statement now.
2. Gather every invoice and receipt, sorted into repairs, fees, insurance, service charges and so on.
3. Get your mortgage interest figure from your lender's annual statement, separate from capital repayments.
4. Split repairs from improvements and keep the improvement invoices safely for the future.
5. Note any replaced furnishings with receipts.
6. Check whether you need payments on account, and budget for 31 January and 31 July.
7. Check whether Making Tax Digital applies to you from April 2026 or April 2027.
8. Book your accountant early. December appointments are easier to get than late-January ones.
9. File and pay before 31 January 2027. Earlier is better: if something is wrong, you have time to fix it.

This is general information, not tax advice. Your position depends on your own circumstances, so please speak to an accountant or tax adviser.