If you had new income during the 2025/26 tax year that HMRC does not already know about, you may need to register for Self Assessment by 5 October 2026.

This deadline often catches people out precisely because it applies to those who do not think of themselves as needing to file a tax return.

It is not about filing or paying, instead it is about telling HMRC whether a tax return is needed at all.

This deadline applies to:

• Anyone who became self-employed during 2025/26 and has not registered before.
• Landlords with new rental income to declare for the first time.
• Anyone with other untaxed income, such as dividends, or a household affected by the High Income Child Benefit Charge for the first time.
• Anyone who stopped filing a return in previous years but now has income that brings them back within Self Assessment.

If you have filed a Self Assessment return for the previous tax year already, you do not need to register again.

HMRC will continue to expect a return from you each year until you formally leave Self Assessment.

Why it is worth acting now

Registering late does not stop you from filing, but it is treated as a failure to notify and can lead to a penalty geared to the tax eventually found to be owed, even where the amount involved is modest.

Registering also takes time to process. HMRC issues a Unique Taxpayer Reference once registration is complete and this can take a couple of weeks to arrive by post, so leaving it until close to the deadline adds unnecessary pressure ahead of the 31 January filing date.

If you think you may need to register for Self Assessment for the first time, or are not sure whether your circumstances require it, contact us well before 5 October and we will take care of the registration for you.

From September 2026, HMRC will begin signing up taxpayers to Making Tax Digital (MTD) for Income Tax where it believes they should already be in the regime but have not registered themselves.

This affects anyone with combined gross income from self-employment and property above £50,000 in 2024/25, unless an exemption applies.

HMRC estimates that up to 294,000 taxpayers could fall into this group, out of an expected first-wave population of around 864,000.

Why signing up yourself is better

It remains possible to sign up voluntarily, or for an agent to sign up a client, right up until HMRC intervenes. Doing so before HMRC acts has real advantages.

• You retain control over the details recorded, including business names and descriptions, which are far harder to correct once HMRC has processed the sign-up itself.
• For clients with more than one business or property, ensuring each is clearly named and distinguished in software is one of the biggest practical lessons from the first quarter.
• Agents are not notified when HMRC signs a client up directly, so proactive registration is the only way to have certainty over a client’s status.

HMRC plans to sign up taxpayers in stages from September, pausing the process around the Self Assessment filing deadline of 31 January 2027.

What we are doing

We are reviewing our client base now to identify anyone who may fall within scope but has not yet signed up, rather than waiting for HMRC’s letters to start arriving.

If you think this might apply to you, or you are simply unsure whether MTD for Income Tax applies to your circumstances, get in touch and we will check your position and, if needed, get you signed up on your own terms.

HMRC has continued its long-running campaign to identify landlords with undeclared rental income and recent activity shows just how much data it now draws on to do so.

Behind most of the letters landlords receive sits HMRC’s Connect system, which pulls information from more than 60 government and third-party sources to build a detailed picture of a person’s financial position.

The information that it uses can come from a variety of sources, including:

• The Land Registry, which flags property purchases, transfers and changes to title deeds.
• Tenancy deposit schemes, since a registered deposit creates a digital record that a property is being let.
• Letting agents, who are required to provide HMRC with details of the landlords they act for.
• Online platforms such as Airbnb and Booking.com, which now report income data directly to HMRC.
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None of these sources proves on its own that income has gone undeclared but taken together they build a pattern that could lead to a nudge letter through your door.

What a nudge letter means

A nudge letter is not a formal enquiry and does not mean a criminal investigation is underway.

It is a prompt inviting the recipient to review their position and come forward voluntarily through HMRC’s Let Property Campaign if anything needs correcting.

Landlords who do come forward voluntarily generally receive far better terms than those who wait for HMRC to open a formal enquiry, both in terms of penalties charged and the tone of any subsequent contact.

With the Let Property Campaign continuing to recover over £100 million a year from landlords and MTD for Income Tax now bringing many landlords into more frequent digital reporting, this is a good time to make sure rental income has been fully and correctly declared.

If you have received a letter from HMRC about rental income or simply want to check your position before HMRC gets in touch, speak to us.

A Personal Tax Account is a free online service from HMRC that gives you direct access to your own tax position, without needing to phone HMRC or wait for a letter to arrive.

If you haven’t created one already, then it is worth setting one up even if you already have an accountant, as it gives you visibility of things that we may not always see and lets you act quickly where something needs attention.

What you can do through your account

There are a variety of useful things that you can do via your account, once it is set up, including:

• Checking your current tax code to see exactly how HMRC has calculated it, including any adjustments for benefits or previous underpayments.
• Claiming a credit balance sitting on your Self Assessment account. This is worth knowing about in particular, since changes to HMRC’s systems mean agents can no longer always do this on a client’s behalf, so it may need to be done directly.
• Seeing an estimate of your tax liabilities coming up, giving you time to plan and set money aside rather than being caught out in January.
• Viewing your National Insurance record, check your State Pension forecast and update personal details such as your address.
• Checking for and claiming a tax refund online, rather than waiting for HMRC to identify an overpayment and write to you.

Signing up is straightforward

You will need to verify your identity, usually using a passport or driving licence, but the process only takes a few minutes and gives you ongoing access once it is complete.

You can set up or sign in to your Personal Tax Account at www.gov.uk/personal-tax-account 

If anything you see in your account raises a question, whether that is a tax code, a credit balance or an upcoming liability, come and talk to us about it before taking action.

HMRC can issue a new tax code several times in a single year and it is easy to assume that each one has been checked and is correct.

In practice, coding notices are often generated automatically and can contain errors that go unnoticed for months having a significant impact on a person’s take home pay.

A new code is frequently triggered once a tax return has been submitted, as HMRC updates its estimate of your income and allowances for the current year based on the figures just filed.

Agents can be kept out of the loop

One point worth flagging directly, which many taxpayers don’t realise, is that a coding notice sent to you is not always copied to your accountant or tax agent at the same time or at all.

HMRC’s systems do not automatically keep agents informed every time a client’s code changes, which means a new or incorrect code can be operated by an employer or pension provider for weeks before anyone supporting you has sight of it.

If your code changes and we are not aware of it, we cannot check it on your behalf, which is why responsibility for spotting a wrong code, at least in the first instance, sits with the taxpayer who receives the notice.

What to look out for

When a new coding notice arrives, whether by post or in your Personal Tax Account, it is worth taking a few minutes to check it against what you expect.

Here is what to look out for:

• The personal allowance and any adjustments shown and whether they still reflect your current circumstances.
• Any entries for benefits in kind, such as a company car, private medical insurance or untaxed interest, that may be out of date.
• Whether an estimated underpayment or overpayment from a previous year has been added to the code and whether the figure looks right.
• The overall code itself, checked against your latest payslip to confirm your employer is actually using it.

A wrong code left in place for a full tax year can mean months of overpaid or underpaid tax and underpayments in particular have a habit of arriving as an unwelcome surprise later on.

If you receive a new coding notice and are not sure whether it is correct, send us a copy as soon as it arrives.

We would rather check it with you now than untangle a problem with HMRC further down the line.

The first quarterly update under Making Tax Digital (MTD) for Income Tax fell due on 7 August 2026, covering the period from 6 April to 5 July for most sole traders and landlords with qualifying income above £50,000.

With that first deadline now behind us, a clearer picture is emerging of how the new system is working in practice and where the pinch points are likely to sit as we move towards the next quarterly update on 7 November.

The numbers tell part of the story

HMRC had expected around 864,000 sole traders and landlords to be mandated into MTD from April. In the end, roughly 570,000 signed up and just over 436,000 filed a first quarterly update.

That gap matters, as it means that a significant proportion of the expected population has either not signed up at all or signed up without yet submitting a return, which is why HMRC has confirmed it will begin signing up outstanding taxpayers itself from this month.

Where the friction has been

For firms and clients who have been through the process, a few recurring issues have stood out.

• Software onboarding took longer than expected, particularly for clients moving from spreadsheets to bridging software or a full bookkeeping package for the first time.
• Businesses with more than one trade or property portfolio needed clear, distinguishing names and descriptions set up in software from the outset, since these are far harder to correct once HMRC has processed a submission.
• Some clients treated the update as a full tax return and tried to make accounting adjustments before sending it, when in fact it is simply a summary of income and expense totals for the quarter.
• Digitally excluded clients and those with genuinely complex affairs needed early conversations about exemptions, rather than leaving the question until the deadline was close.

What this means for the next quarter

There are no penalty points for late quarterly updates during the 2026/27 tax year, which has taken some of the pressure off this first cycle, but it is still the legal duty of taxpayers, even if there is no immediate penalty.

That grace period will also not last indefinitely and the record-keeping habits built now will matter once penalties do apply.

If you are still finding your feet with MTD, or have not yet submitted your first update, get in touch.

We can help you choose the right software and get your records in order well ahead of the next deadline.