For the self-employed, January is rarely a quiet month. Between chasing outstanding invoices and managing the post-Christmas lull, HMRC is waiting — and it has very little patience for late returns. The 2025/26 tax year brings the same immovable deadlines as always, but with Making Tax Digital for Income Tax Self Assessment (MTD for ITSA) continuing its phased rollout, the landscape is shifting in ways that affect sole traders and landlords more than ever. This checklist covers every critical date, the records you need to gather, and the practical steps that will keep penalties firmly off your desk.
Key ITSA Dates for the 2025/26 Tax Year at a Glance
The 2025/26 tax year runs from 6 April 2025 to 5 April 2026. The deadlines that follow relate to the 2024/25 tax year return — the one you'll be filing during 2025. It's a common point of confusion, so pin this to your wall.
- 5 April 2025 — End of the 2024/25 tax year. Stop adding income and expenses to the wrong year from this date.
- 6 April 2025 — Start of the 2025/26 tax year. New record-keeping period begins.
- 31 July 2025 — Second payment on account for 2024/25 due. If you made payments on account in January 2025, the second instalment falls here.
- 5 October 2025 — Deadline to register for Self Assessment if you became self-employed during 2024/25 and haven't registered yet. Missing this triggers an automatic penalty.
- 31 October 2025 — Deadline for paper Self Assessment returns for 2024/25. Paper filing is becoming increasingly rare, but if you or your client still use it, this date is non-negotiable.
- 30 December 2025 — Deadline to submit your 2024/25 online return if you want HMRC to collect tax owed via PAYE coding (provided the amount is under £3,000 and you have a PAYE income source).
- 31 January 2026 — The big one. Online Self Assessment return and balancing payment for 2024/25 due, plus the first payment on account for 2025/26.
Miss 31 January and HMRC charges an immediate £100 fixed penalty — regardless of whether you owe any tax. After three months, daily £10 penalties accumulate for up to 90 days. After six months and twelve months, further percentage-based surcharges apply. It adds up very quickly.
What Records You Need to Pull Together
Good record-keeping throughout the year is what separates a stress-free January from a panicked scramble. HMRC expects you to retain business records for at least five years after the 31 January filing deadline — that's five years from January 2026 for the 2024/25 return.
Here's what to gather before you or your accountant can complete the return:
- Income records: All invoices raised, sales summaries, bank statements, PayPal or Stripe transaction exports, and any cash income logs.
- Expenses: Receipts and invoices for allowable business costs — office supplies, travel, professional subscriptions, subcontractor payments, and so on. Remember, business use of home claims require a calculation, not just a guess.
- Bank statements: Full statements for all business (and relevant personal) accounts covering 6 April 2024 to 5 April 2025.
- Mileage logs: If you're claiming the HMRC approved mileage rate (45p per mile for the first 10,000 miles, 25p thereafter), you need a contemporaneous log — not one written retrospectively in January.
- P60s and P45s: If you also have employed income, your employer's documents are required.
- Dividend vouchers and rental income statements: Relevant if your income picture is mixed.
- Previous Self Assessment statements: To confirm payments on account already made.
Tools like BizHub365 make this considerably easier. Its AI-powered receipt scanning — built on Anthropic Claude — lets you photograph receipts on the go throughout the year, automatically categorising expenses so there's nothing left to reconstruct in January. Bank statement import means your bookkeeping stays live, not retrospective.
Payments on Account: The Trap That Catches New Sole Traders
Payments on account are advance payments towards your next year's tax bill. HMRC requires them when your previous year's Self Assessment tax liability exceeds £1,000 and less than 80% of your tax was deducted at source (e.g., through PAYE).
Each payment on account is 50% of your previous year's liability, due on 31 January and 31 July. So if your 2024/25 tax bill comes to £4,000, you'll pay £4,000 on 31 January 2026 plus a first payment on account of £2,000 — a total of £6,000 in one hit. Many new sole traders are blindsided by this.
If you believe your 2025/26 income will be lower, you can apply to reduce your payments on account via HMRC's online portal or through your accountant. Just be careful: if you reduce too aggressively and your actual liability is higher, HMRC charges interest on the shortfall. Set aside at least 25–30% of your net profit throughout the year as a tax reserve to avoid a cash crisis.
MTD for ITSA: What's Coming and Who's Affected
Making Tax Digital for Income Tax Self Assessment is HMRC's long-term plan to replace the annual Self Assessment return with quarterly digital reporting. The phased rollout is as follows:
- April 2026: Sole traders and landlords with qualifying income over £50,000 must comply.
- April 2027: Those with qualifying income over £30,000 must comply.
- April 2028: Those with qualifying income over £20,000 must comply (subject to final confirmation).
Under MTD for ITSA, you'll submit quarterly updates to HMRC from compatible software, followed by an end-of-period statement and a final declaration replacing the current Self Assessment return. The annual deadline structure we know today will look very different for affected taxpayers within two to three years.
If you're approaching the £50,000 threshold, now is the time to ensure your software is MTD-compatible. BizHub365 supports direct HMRC API submission — no bridging software required — meaning the transition to quarterly reporting can happen without disrupting your existing workflow.
Your Pre-Filing Checklist: Practical Steps to Take Now
Rather than waiting until November or December, here's a practical action plan you can start today:
- Confirm your UTR is active. Your Unique Taxpayer Reference is on previous HMRC correspondence. If you've lost it, retrieve it via your HMRC online account. Without it, you cannot file.
- Check your Government Gateway credentials. Log in now, not on 30 January 2026, to confirm your password and authenticator app are working. HMRC's login systems can slow significantly as the January deadline approaches.
- Reconcile your accounts for 2024/25. Match your income records against bank statements. Investigate every discrepancy.
- Review allowable expenses. Consider whether you've claimed the annual investment allowance for equipment, used the £1,000 trading allowance (if applicable), or claimed pension contributions for tax relief.
- Speak to your accountant early. Accountants are considerably more available in October than in January. An early conversation also gives time to plan — for example, making additional pension contributions before 5 April to reduce your tax liability.
- Set a personal deadline of 31 December. Give yourself a full month's buffer before the official online deadline. If something goes wrong — an HMRC technical error, a missing document — you'll have time to fix it.
Conclusion: Deadlines Don't Move, But Your Preparation Can
HMRC's Self Assessment deadlines are fixed. The penalties are automatic. But the stress that surrounds them every January is entirely optional — and it stems almost entirely from leaving things too late. Whether you're a sole trader running a landscaping business in Leeds, a freelance graphic designer in Bristol, or an accountant managing dozens of client returns, the principle is the same: spread the workload across the year, keep your records current, and treat 31 January as a confirmation date rather than a starting gun.
The 2024/25 return is your immediate priority. But with MTD for ITSA on the horizon, 2025 is also the year to assess whether your current systems will hold up under quarterly reporting obligations. If they won't, it's worth exploring platforms like BizHub365 that are built for exactly that future — direct HMRC API integration, live bookkeeping, and compliance tools designed around the way UK small businesses actually operate.
File early. Keep records throughout the year. And never, ever leave your UTR somewhere you can't find it.