Swift Accountants
The key dates you need — explained clearly, with no jargon.
f you’re searching “Self Assessment deadline”, you’re not alone. The UK tax calendar has a few critical dates — and missing the wrong one can trigger penalties, interest, or unnecessary stress.
This guide covers the key Self Assessment filing deadlines, payment deadlines, the PAYE tax code option, and what to do if you’re late — plus a fixed-fee option if you want it handled for you.
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Here are the standard UK deadlines most people need to know:
– 5 October: Tell HMRC you need to file (new to Self Assessment/need to start filing again)
– 31 October: Paper tax return deadline (HMRC must receive it)
– 30 December: File online by this date if you want HMRC to collect what you owe through your PAYE tax code (only if eligible)
– 31 January: Online tax return deadline (late filing penalties apply after this)
– 31 January: Tax payment deadline (balancing payment is due)
– 31 July: Second payment on account deadline (only if payments on account apply)
Official deadlines are set by HMRC, and exact dates depend on the tax year you’re filing for.
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Need help with Self Assessment? If you’d rather not risk deadlines, penalties, or confusion, we can handle your Self Assessment tax return on a fixed fee — tidy records, clear calculations, and fast answers in plain English.
Self Assessment Tax Return Service (fixed fee, done-for-you)
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– you submitted your paper return by 31 October or your online return by 30 December
If you miss the deadline (or don’t meet the criteria), you’ll need to pay by another method.
Payments on account are advance payments towards your next tax bill. If they apply to you, you’ll typically pay:
– First payment on account: 31 January
– Second payment on account: 31 July
This often makes January feel expensive because you may be paying your tax for the year PLUS an advance payment for the next year.
If you’re unsure whether payments on account apply, we can confirm quickly and help you plan what to set aside.
You can submit your Self Assessment tax return any time after the tax year ends (the tax year runs 6 April to 5 April). Filing early helps you:
– see what you owe sooner
– plan cashflow
– avoid last-minute mistakes and missing documents
If you file late, HMRC can charge late filing penalties, starting with an initial £100 penalty. Further penalties may apply if it remains late.
Important: you can still get the £100 penalty even if you don’t owe any tax — so it’s worth filing as soon as possible to stop penalties escalating.
If you’re late right now, your best move is simple:
1) file the return (stop late filing penalties from getting worse)
2) confirm what’s owed
3) pay what you can, and explore options early if you can’t pay in full
Late payment penalties (if you pay late)
HMRC can charge late payment penalties of 5% of the tax unpaid at:
– 30 days
– 6 months
– 12 months
Interest is also charged on the amount owed.
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If you can’t pay in full, HMRC may allow a “Time to Pay” arrangement in some cases.
Key point: HMRC states you cannot set up a Time to Pay arrangement until the Self Assessment return has been filed. For some cases, an online payment plan may be available if the debt is under £30,000 and you meet the criteria — otherwise you may need to contact HMRC directly.
The best approach is always acting early rather than ignoring it — because late payment penalties and interest can apply.
– Waiting until January to look for paperwork
– Forgetting payments on account exist (so January feels “double”)
– Assuming “I’ll just file later” (penalties can apply even if there’s no tax due)
– Missing the 30 December cut-off for paying through your PAYE tax code (if eligible)
– Not telling HMRC by 5 October if it’s your first time filing (or you need to restart filing)
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For most people, the online deadline is 31 January after the end of the tax year.
For most people submitting a paper return, HMRC must receive it by 31 October.
The main payment deadline is 31 January. If payments on account apply, there’s usually another payment deadline on 31 July.
If you need to file for the first time (or need to start filing again), you usually need to tell HMRC by 5 October after the end of the tax year.
If you want HMRC to collect what you owe through your PAYE tax code (where eligible), you must usually file your online return by 30 December.
Yes. A late filing penalty can still apply even if there is no tax to pay — so it’s worth filing as soon as possible.
HMRC can charge penalties for late filing, starting with an initial £100 penalty, with further penalties if it remains late.
In some cases, you may be able to arrange a Time to Pay plan — the key is filing the return first and acting early.
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Straight-talking accounting — built around compliance, clarity, and proactive support.
We focus on long-term relationships, not quick transactions. We chase what’s needed early so deadlines don’t become drama. Clients tell us they save more tax because we plan properly, not just file and forget. Switching is smooth because we manage the handover from start to finish — and clients recommend us because they feel genuinely looked after.
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With Swift Accountants, you’re not just planning for success — you’re building it with clarity, control and confidence.
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When your finances feel unclear, it affects everything — your cashflow, your decisions, your time, and your peace of mind.
That’s why we work in a genuinely human way. We listen first, then explain what matters in plain English — without jargon and without making you feel like you “should already know”.
You’ll know where you stand, what’s happening next, and what we need from you (if anything). And if there’s a real opportunity to save tax or improve the way things run, we’ll tell you — clearly and honestly.
If you want calm, responsive accountants who are on your side, let’s talk. Coffee’s on us if we meet ☕
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Need to talk it through? Call us and speak to a real person — no robots, no endless menus. Just clear answers and practical help.
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We go further, respond faster, and work harder for you. Join hundreds of UK businesses who trust us with their financial future—and discover the difference a true accounting partner can make.
Experience a True Partnership—Where You Come First, Always
At Swift Accountants, you’re never just another client. We make accounting feel simpler, clearer and more organised from day one, whether you need bookkeeping, VAT (MTD), payroll, Self Assessment, or limited company accounts.
Manage your accounts, VAT, payroll and documents in one secure portal — upload paperwork, approve documents, and track progress anytime.
Clear monthly pricing with no hidden extras. Unlimited questions included, so you can get advice when you need it.
Switching is simple. We manage the handover end-to-end, keep everything moving, and make sure nothing gets missed.
A dedicated accountant who understands your situation and gives clear, practical guidance — big questions or small.
Every great business story starts with a single conversation. That chat is absolutely free—and may be the moment that changes your business’s future.
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However you contact us — phone, email, WhatsApp, portal, or in person — you’ll get clear answers from real people who care about your business and your deadlines.
Our team has deep expertise across a range of industries and sectors, meaning your finances are managed by professionals who truly understand your business and goals. We stay ahead of the latest tax rules, legislation, and opportunities, so you never miss out.
We’re here for more than just your accounts. With proactive, year-round advice, we help you boost profits, reduce tax, and make smarter business decisions. Our focus is on helping you not only stay compliant but grow, thrive, and achieve more.
Your financial information is protected with secure systems, access controls and encrypted storage. We follow GDPR requirements and treat your data with care.
At Swift Accountants, we’re here to make accounting feel simpler, clearer and more controlled. You’ll get fixed fees, a dedicated accountant, and proactive support — so you stay compliant, avoid surprises, and make decisions with confidence as your business grows.
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Our Commitment to Excellence
At Swift Accountants, excellence is more than a goal; it’s our promise. We’re dedicated to providing our clients with the highest level of professionalism and integrity. Our proactive approach helps you stay ahead of your financial commitments while making the most of your resources.
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Every client is unique, and we take the time to understand your specific needs. Our experts craft tailored strategies that align with your business goals.
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