Self Assessment deadlines for sole traders and landlords

If you are a sole trader or a small landlord, the Self Assessment calendar is the backbone of your tax year. Miss a date and you can face automatic penalties even when no tax is due. Get ahead of it and January stops being a scramble.

This note sets out the standard UK Self Assessment deadlines, how payments on account work, and what to gather for a smooth sole trader tax return — whether you are based in Chislehurst, Bromley, Orpington, Sidcup or Swanley, or work with us remotely across the UK. It is general guidance only; your circumstances may differ, so confirm dates in your HMRC online account and take advice where you need it.

The tax year and the two filing clocks

The UK tax year runs from 6 April to 5 April. For Self Assessment you usually file for the year that has just ended. Taking the 2025–26 tax year (ended 5 April 2026) as the current cycle:

• Paper return — HMRC must receive it by 31 October 2026.
• Online return — submit by 31 January 2027.
• Balancing payment — any tax still owed for that year is normally due by 31 January 2027 as well.

Most people file online. Paper is still available, but the earlier deadline and slower calculation process make it a poor default unless you have a specific reason. If you want HMRC to collect a balancing amount through PAYE (where that option applies), you typically need to file online by 30 December following the tax year — check GOV.UK for the exact conditions.

New to Self Assessment? You normally need to register in time so HMRC can issue your Unique Taxpayer Reference (UTR). As a rule of thumb, register by 5 October after the end of the tax year you need to report. Registering late can change your filing deadline, but it does not usually move the 31 January payment date — so do not treat late registration as more time to pay.

Payments on account: 31 January and 31 July

Alongside the balancing payment, many people make payments on account towards the next year’s bill. In outline:

• Two equal instalments, due by midnight on 31 January and 31 July.
• Each instalment is normally half of the previous year’s Income Tax and Class 4 National Insurance (where relevant), as calculated on your last return.
• You may not need them if last year’s relevant tax was under £1,000, or if more than 80% of your tax was already collected outside Self Assessment (for example through PAYE).

On 31 January you can therefore face both a balancing payment for the year just filed and the first payment on account for the year ahead. That is why January cash-flow planning matters for sole traders and landlords with variable income.

If you know this year’s profit will be lower, you can ask HMRC to reduce payments on account — but only to a realistic estimate. Under-paying and then correcting later can attract interest. If profits rise, you may still owe more at the next balancing date. Your HMRC Self Assessment statement is the source of truth for amounts due.

What sole traders should prepare

A tidy sole trader tax return starts with records, not software. Aim to have the following ready well before you (or your accountant) open the return:

• Bank statements and a clear record of business income
• Receipts and notes for allowable expenses
• Vehicle, home-office or other apportionment workings if you claim them
• Details of any CIS deductions, grants or other income
• Capital purchases that may qualify for allowances
• Pension contributions, Gift Aid and other personal adjustments that affect the bill

Making Tax Digital for Income Tax is rolling out in phases for those within the thresholds. Even before your MTD start date, digital records and compatible software make January faster and reduce errors. Our insight on Making Tax Digital for Income Tax explains the direction of travel; our sole trader / self-assessment service covers day-to-day support.

Landlords: property income on the same calendar

UK property income (and many overseas property situations) is usually reported on Self Assessment using the same filing and payment dates. Landlords should gather:

• Rental statements and tenancy details
• Allowable property expenses and finance costs (rules differ from older interest relief)
• Capital works versus repairs — keep invoices clear
• Joint ownership shares and any Form 17 elections where relevant
• Furnished holiday let or other regime details if applicable

If you are both a sole trader and a landlord, everything still sits on one return and one set of payment dates. That is often where January surprises come from — two income streams, one balancing bill.

A simple calendar you can stick on the fridge

1. April–May — close the tax year books; list missing invoices.
2. Summer — draft figures; check whether July’s payment on account still looks right.
3. By 31 October — paper filers must be done (most people should already be online).
4. November–December — finalise the online return; plan January cash.
5. By 30 December — file if you need PAYE coding collection where available.
6. By 31 January — file online, pay the balance, and pay the first payment on account if due.
7. By 31 July — second payment on account if due.

Late filing attracts an automatic £100 penalty, with further charges the longer the return stays outstanding. Late payment attracts interest and, in time, further penalties. If cash is tight, speak to HMRC or your accountant early about options such as a payment plan — silence until the due date is usually the expensive choice.

Local help without the jargon

We work with sole traders and landlords from our base at 1 Bromley Lane, Chislehurst, and with clients across Bromley, Orpington, Sidcup, Swanley and the wider UK remotely. If you are comparing firms, our guide to choosing an accountant in Chislehurst sets out practical questions to ask. For ongoing support, see accountants in Chislehurst and accountants in Bromley.

How Muftals can help

As ACCA and CIMA accountants we prepare Self Assessment returns, review expenses and map your payment dates in plain English — without invented one-size-fits-all fees. Explore sole trader / self-assessment or book a free meeting. Call 0207 078 7546 or email info@muftalsaccountancy.co.uk. Confirm critical amounts and deadlines with HMRC or your adviser if your situation is non-standard — this article is not personal tax advice.