The 2025/26 tax year has ended, and the clock is now running on closing your final checks. Whether you are a sole trader, a company director, or a landlord, understanding the key dates and updated thresholds helps you prepare accurately for post-year action. All deadlines and thresholds on this page are drawn from HMRC’s self assessment guidance on GOV.UK.
The Critical Dates for 2025/26
Mark these in your calendar and treat them as firm deadlines, not guidelines:
- 5 April 2026: end of the 2025/26 tax year
- 5 October 2026: deadline to register for self-assessment if you are newly self-employed
- 31 October 2026: deadline to file a paper tax return
- 31 January 2027: deadline to file online, pay your tax bill, and make your first payment on account
- 31 July 2027: deadline for your second payment on account
The online filing deadline is the one most people focus on, and for good reason: missing it triggers an automatic penalty regardless of whether you owe any tax.
Who Must File a Self-Assessment Return
You are required to file if any of the following apply to you in 2025/26:
- You are self-employed and earned over £1,000 gross (the trading allowance threshold; below this, you may not need to register)
- You are a company director receiving income that has not been taxed at source
- You are a landlord with rental income
- Your household received Child Benefit and either you or your partner earned over £60,000 (the High Income Child Benefit Charge threshold)
- You have untaxed savings or investment income above the relevant allowances
If you are unsure whether you need to file, err on the side of registering. Late registration carries its own penalties, and HMRC takes a dim view of avoidable non-compliance.
What to Gather Before You File
Good record-keeping now saves hours in January. Start pulling together:
- P60 or P45 from any employment in the year, plus any P11D for benefits in kind
- Self-employment records: income, allowable expenses, invoices, receipts, mileage logs
- Dividend income: from any company shares you hold (the dividend allowance is £500 for 2025/26)
- Mileage records if claiming the approved mileage rate (45p per mile for the first 10,000 miles, 25p thereafter)
- Capital gains information if you disposed of assets (shares, a second property, cryptocurrency)
The more organised your records are throughout the year, the less painful the filing process becomes.
Updated Thresholds and Rates for 2025/26
Key figures you need to know for this tax year, all verified against HMRC income tax rates on GOV.UK:
- Personal allowance: £12,570, unchanged from 2024/25
- Basic rate (20%): applies to income between £12,571 and £50,270
- Higher rate (40%): applies to income between £50,271 and £125,140
- Additional rate (45%): applies to income over £125,140
- Dividend allowance: £500
- Capital gains tax exempt amount: £3,000
- Class 2 National Insurance: no longer mandatory from 6 April 2024, but voluntary contributions remain available at £3.50 per week to protect state pension entitlement
- Class 4 National Insurance: 6% on profits between £12,570 and £50,270, 2% on profits above £50,270
The abolition of Class 2 NI simplifies the picture for many sole traders, but it also means the mechanism for building state pension entitlement through self-employment has changed. If your profits fall below the small profits threshold, you may want to make voluntary Class 3 contributions to protect your record.
Payments on Account Explained
If your tax bill is over £1,000 and less than 80% of your tax was collected via PAYE, HMRC requires you to make payments on account: advance payments towards next year’s bill.
Each payment on account is 50% of your previous year’s tax liability. They fall due on 31 January and 31 July. This catches many first-time filers off guard: you may owe your 2025/26 tax bill plus the first payment on account all in one January 2027 payment.
If your income has dropped significantly, you can apply to reduce your payments on account before you file your return using form SA303 or HMRC’s online service.
Penalty Structure
HMRC’s penalty regime for late filing and late payment is straightforward but unforgiving:
Late filing:
- £100 immediately on the day after the deadline, even if you owe nothing
- £10 per day after three months, up to a maximum of £900
- A further 5% of the tax owed or £300 (whichever is greater) at six months
- The same again at twelve months, with additional penalties for deliberate non-compliance
Late payment:
- Interest accrues at HMRC’s current rate from the day after the deadline
- A 5% surcharge on the unpaid tax at 30 days, with further surcharges at six and twelve months
If you cannot pay in full, do not ignore it. HMRC’s Time to Pay arrangement allows you to agree a structured payment plan, but you need to contact them proactively, before enforcement action begins.
Making Tax Digital for Income Tax
MTD for Income Tax is coming, and for many self-employed people and landlords, it will change how you report to HMRC entirely.
From April 2026, MTD for Income Tax becomes mandatory for those with qualifying income over £50,000. From April 2027, the threshold drops to £30,000.
Under MTD, you will be required to keep digital records and submit quarterly updates to HMRC using compatible software, replacing the annual tax return with a more regular reporting rhythm. A final declaration (similar to today’s return) will still be submitted at the end of each year.
You can check if you’re eligible for Making Tax Digital for Income Tax on GOV.UK.
Preparation Checklist
Work through these steps well before January:
- Confirm whether you are required to file for 2025/26. Register by 5 October 2026 if you are newly self-employed
- Reconcile all income sources: employment, self-employment, dividends, rental, savings
- Compile and categorise allowable business expenses with supporting receipts
- Reconcile your mileage log and calculate the approved mileage deduction
- Review any capital disposals during the year and calculate your gain or loss
- Check your student loan repayment status if applicable, as this is reported on the return
- Set aside funds for the January 2027 payment, factoring in your first payment on account if this applies to you
How Page Ivy Can Help
Filing a self-assessment return is straightforward when your records are clean and your income is simple, but most business owners have complexity that warrants professional review. At Page Ivy, we handle self-assessment returns for sole traders, directors, and landlords, making sure you claim everything you are entitled to and pay exactly what you owe, no more.
Whether you need a one-off filing or ongoing support, we can help you stay on the right side of HMRC. Get in touch to find out how we work.
