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Q: What if I missed the 5 October registration deadline?

Register as soon as possible. HMRC may issue a penalty for late registration but this is separate from late filing penalties.

Q: Can I get an extension to 31 January?

Extensions are rare and only for serious illness or bereavement. Plan ahead instead.

Q: What if I can’t afford my tax bill?

Contact HMRC for a Time to Pay plan to spread payments. Interest applies but avoids penalties.

Q: Do I still file if I made no profit?

Yes. You must file even with no profit, and you can carry forward losses.

Self Assessment • UK

31 January is non-negotiable: file and pay your Self Assessment on time

The UK tax year runs from 6 April to 5 April. If you’re self-employed or have untaxed income, you must submit and pay by 31 January. Below is your fully visual, easy-scan guide linked to the Stewart Accounting website.

Get help with your return Who must file?

Key date

Self Assessment deadline

31 January 2025

Covers the 2023–24 tax year (6 Apr 2023–5 Apr 2024).

Do both

File & pay the same day

Submitting without paying (or vice-versa) still triggers penalties and interest.

New to SA?

Register by 5 October

If new to trading, check if you must file and register promptly.

Understanding the Self Assessment timeline

Your earnings between 6 April and 5 April form one tax year. For 2023–24, file and pay by 31 January 2025. Unsure whether you must file? See who must send in a return.

Shortcut

Two recurring checkpoints: 31 January (file, pay & first Payment on Account if due) and 31 July (second Payment on Account).

Talk to Stewart Accounting

Self Assessment support Do I need to file?

Calendar showing 31 January tax deadline

Key Self Assessment deadlines at a glance (2023–24)

Bookmark this: your quick-reference guide.

Task	Deadline	Notes
Tax year ends	5 April 2024	End of reporting period.
Register for Self Assessment	5 October 2024	Crucial for first-time filers.
Paper tax return	31 October 2024	Applies if filing on paper.
Online tax return	31 January 2025	Main deadline for most people.
Pay your tax bill	31 January 2025	Payment due same day as submission.
2nd Payment on Account (if due)	31 July 2025	Typically 50% of previous year’s bill.

Payments on Account (POA) — how they work

If your bill was over £1,000 and less than 80% collected via PAYE, HMRC usually requires two advance Payments on Account—on 31 January and 31 July—each about 50% of last year’s bill.

31 January

File, pay balance, and make first POA.

31 July

Second POA keeps January manageable.

Adjustments

If income falls, apply to reduce POA via Stewart Accounting.

Late filing penalties escalate fast

After 31 Jan: £100 penalty (even if no tax due)
3 months late: £10/day for up to 90 days (max £900)
6 months late: +£300 or 5% of tax (whichever is higher)
12 months late: another £300 or 5%
Interest: accrues from original due date

Missed something? Don’t wait—penalties compound. We’ll help you recover.

Fix late returns

Watch: Self-employed deadline essentials (Quick Overview)

Why people miss the deadline (and how not to)

Disorganisation: Receipts vanish. Fix: Use scanning apps weekly.
Underestimating the work: It’s rarely a one-night job. Fix: Set a personal soft deadline early Jan.
Life happens: Illness or family events. Fix: File early in December for breathing room.

A practical checklist for a timely return

UTR (Unique Taxpayer Reference)
National Insurance number
All income records (invoices, bank, interest)
Allowable expenses (travel, office, fees)
Choose HMRC or software filing
Double-check and keep PDF copy

FAQs: Self Assessment deadlines

What if I missed the 5 October registration deadline?

Register ASAP. HMRC may fine for late registration but it’s separate from late filing penalties. Contact Stewart Accounting for help.

Can I get an extension to 31 January?

Extensions are rare, only for extreme cases (serious illness/bereavement). Build your own buffer instead.

What if I can’t afford my tax bill?

Ask HMRC for a Time to Pay plan to spread payments. Interest applies, but you avoid late-payment penalties.

Do I still file if I made no profit?

Yes. Once registered, you must file—even at a loss. You may carry that loss forward against future profits.

Done right & on time

Let Stewart Accounting handle your Self Assessment from start to finish.

We’ll keep you compliant, minimise penalties, and ensure every allowance is claimed.

Start now