When is the Self Assessment deadline?

The filing deadline is 31 January after the end of the tax year. The payment deadline is the same day — 31 January. There's a second payment on 31 July (payment on account). If you're under Making Tax Digital, you also send quarterly updates on 7 August, 7 November, 7 February, and 7 May — but these are reporting deadlines, not payment deadlines.

What happens if I miss the Self Assessment deadline?

You get an automatic £100 late filing penalty, even if you owe no tax. After 3 months, £10/day is added (up to £900). At 6 and 12 months, a further £300 or 5% of tax due is charged. Interest accrues on unpaid tax from 1 February. File as soon as possible to stop penalties escalating — see our missed deadline guide for the full process.

Can't pay your Self Assessment tax bill?

Set up a Time to Pay arrangement with HMRC — online if you owe under £30,000, or by calling 0300 200 3835 for larger amounts. This suspends the 5% late payment surcharges at 30 days, 6 months, and 12 months. Interest still accrues. See our Time to Pay guide for the full setup, or our can't afford tax bill guide if your situation is more serious.

What if I can't access my Self Assessment account?

If you've lost your UTR, recover it through HMRC. If you're locked out of Government Gateway, reset your credentials. If you can't access the online service at all, see our can't access Self Assessment guide. Don't let an access problem stop you from filing — the penalties keep accruing even if you can't log in.

How do I appeal a Self Assessment penalty?

File your return and pay your tax first, then appeal online through your HMRC account or by post using form SA370. You need a reasonable excuse — serious illness, bereavement, HMRC system failure, or events beyond your control. HMRC aims to respond within 45 days. See our appeal HMRC penalty guide for the full process.

What should I do first if I've missed multiple deadlines?

Triage in this order: 1) File your return now — the filing penalty stops escalating the moment you submit. 2) Pay what you can — this reduces interest and shows good faith. 3) Set up a Time to Pay plan for the rest. 4) Appeal penalties if you have a reasonable excuse. 5) Claim any refunds or reliefs you missed. Don't freeze — the penalties get worse every day you wait.

Self Assessment Deadlines, Penalties, and Payment: What to Do and When

The 31 January Self Assessment deadline is the single biggest source of panic for sole traders, landlords, and freelancers in the UK. Miss it and the penalties start automatically — £100 the day after, £10/day after 3 months, and surcharges on top. If you also can’t pay the tax bill, the problem compounds. And if you can’t even access your HMRC account to file, the penalties keep accruing while you’re locked out.

This hub maps every deadline, penalty, and payment problem in one place. Each section gives you the essentials in a few sentences, then links to the detailed guide for the deep dive. If you’ve missed multiple deadlines, the final section tells you what to do first.

1. The Self Assessment Deadline Calendar (2026/27)

Self Assessment has two types of deadline: filing/payment deadlines and (under Making Tax Digital) reporting deadlines. They run in parallel and don’t merge.

Deadline	Date	What happens
Filing deadline	31 January 2027	Submit your 2025/26 Self Assessment return (or final declaration under MTD)
Payment deadline	31 January 2027	Pay your balancing payment + first payment on account
Payment on account	31 July 2027	Second payment on account for the current year
MTD quarterly update 1	7 August 2026	Q1 summary (reporting only, no payment)
MTD quarterly update 2	7 November 2026	Q2 summary
MTD quarterly update 3	7 February 2027	Q3 summary
MTD quarterly update 4	7 May 2027	Q4 summary

The key distinction: filing and payment deadlines have penalties for missing them. MTD quarterly updates are reporting only — no money is due. During the 2026/27 soft landing, there are no penalties for late quarterly updates, but you still need to submit them before your final declaration.

For the full MTD deadline calendar and what each quarterly update contains, see our MTD quarterly updates guide. For how the tax year works and why 31 January is the deadline, see our UK tax year explained guide.

2. Missed the Filing Deadline? What Happens Next

The day after the 31 January deadline, HMRC issues an automatic £100 late filing penalty — even if you owe no tax or are due a refund. The penalties then escalate:

3 months late: £10/day for 90 days (up to £900)
6 months late: £300 or 5% of tax due (whichever is higher)
12 months late: another £300 or 5% of tax due — can rise to 100% for deliberate withholding

The most important thing: file as soon as possible. The daily penalty stops the moment you submit. You can still file online — the deadline is for submission, not a cut-off. For the step-by-step process of what to do after you’ve missed the deadline, see our missed Self Assessment deadline guide. For the full consequences of filing late (including what happens to your tax code and credit file), see our filed late what happens guide.

3. The Full Penalty Ladder: Filing and Payment

Self Assessment has two separate penalty regimes that run independently. You can be hit by one, both, or neither.

Late filing penalties: £100 (1 day late) → £10/day (3 months) → £300 or 5% (6 months) → £300 or 5% (12 months). These are fixed — they apply regardless of how much tax you owe.

Late payment penalties: 5% surcharge on unpaid tax at 30 days, 6 months, and 12 months, plus interest at 7.25% (variable, set by HMRC). Interest accrues daily and is not suspended by a payment plan.

The two regimes stack: if you file late AND pay late, you get both sets of penalties. For the complete penalty ladder with worked examples at each stage, see our Self Assessment penalties guide. You can also use our penalty calculator to estimate your total.

4. Can’t Pay Your Tax Bill? Your Options in Order

If you can’t pay your Self Assessment bill, you have a hierarchy of options — and the earlier you act, the more options you keep.

Pay in full if you can — this stops all interest and penalties.
Set up a Time to Pay arrangement — online if you owe under £30,000, or by calling HMRC’s Payment Support Service on 0300 200 3835. This suspends the 5% late payment surcharges (but not interest).
Reduce your payments on account if your income has dropped — this reduces your 31 July bill, but be careful: if you reduce too far, you’ll owe the difference plus interest.
Seek free debt advice if the tax debt is part of a wider debt problem — StepChange, National Debtline, or Citizens Advice.

The worst option is ignoring it. HMRC can collect via your tax code, send bailiffs (Distraint without a court order), file a County Court Judgment, or petition for bankruptcy. For the full payment options guide, see our can’t afford tax bill guide. For the Time to Pay setup process specifically, see our HMRC payment plan time to pay guide.

5. The 31 July Payment on Account Problem

Payments on account are advance payments toward your next year’s tax bill — due on 31 January and 31 July. If your income has dropped, the 31 July payment can be a nasty surprise because it’s based on your previous year’s profit.

You can reduce your payments on account through your HMRC online account if you expect your income to be lower. But if you reduce too far and your actual bill turns out higher, you’ll owe the difference plus interest. For what payments on account are and how they work, see our payment on account explained guide. For what to do if you can’t pay the 31 July bill, see our can’t pay payment on account guide.

6. Can’t Access Your Account to File?

Sometimes the problem isn’t filing or paying — it’s that you can’t get into your HMRC account in the first place. The penalties keep accruing while you’re locked out, so resolve the access problem fast.

Lost your UTR? You need your Unique Taxpayer Reference to file. Recover it through HMRC — see our lost UTR number guide for every recovery method.
Locked out of Government Gateway? Reset your credentials or set up a new account — see our locked out of Government Gateway guide.
Can’t access the online service at all? If the HMRC portal is down or your account is blocked, see our can’t access Self Assessment guide.

Don’t wait for the access problem to resolve itself — call HMRC on 0300 200 3310 if you’re stuck. The filing deadline doesn’t move because you can’t log in.

7. How to Appeal a Self Assessment Penalty

If you have a reasonable excuse for filing or paying late, you can appeal the penalty. HMRC accepts:

Serious illness or hospitalisation
Bereavement
HMRC system failure or online service outage
Events beyond your control (fire, flood, theft)
Postal delays (for paper returns)

You must file your return and pay your tax first, then appeal. The appeal can be made online through your HMRC account or by post using form SA370. HMRC aims to respond within 45 days. For the full appeals process, including what counts as a reasonable excuse and how to structure your appeal letter, see our appeal HMRC penalty guide.

8. If You’ve Missed Multiple Deadlines: Triage

If you’ve missed the filing deadline, can’t pay the bill, and have penalties stacking up, the situation feels overwhelming. Here’s the order to tackle it:

File your return now. This is the single most important step. The £10/day penalty stops the moment you submit. Even if you can’t pay, filing stops the filing penalties from escalating further. File online through your HMRC account — if you can’t access it, see section 6 above.
Pay what you can. Even a partial payment reduces the interest accruing and shows HMRC you’re engaging. The 5% surcharges are calculated on the unpaid balance, so every pound you pay reduces future surcharges.
Set up a Time to Pay plan for the rest. Do this before the 30-day surcharge hits. See our Time to Pay guide for the setup process.
Appeal penalties if you have a reasonable excuse. File first, then appeal. See our appeal guide for what counts.
Check for refunds or reliefs you missed. If you forgot to claim expenses, pension contributions, or other reliefs, amend your return within 12 months of the filing deadline. See our fixing mistakes guide for the amendment process.
If you never registered for Self Assessment, a different penalty regime applies (“failure to notify”) — often £0 if you owed no tax. See our didn’t know I needed to register guide.

The key: don’t freeze. Every day you wait, the penalties get worse. File today, pay what you can, and deal with the rest through a plan or appeal.

The Bottom Line

31 January is the big deadline — filing and payment on the same day. 31 July is the second payment on account.
File immediately if you’ve missed the deadline. The £10/day penalty stops the moment you submit.
Two penalty regimes run independently — late filing and late payment. You can be hit by both.
Time to Pay suspends surcharges but not interest. Set it up before the 30-day surcharge hits.
Access problems don’t pause penalties. Recover your UTR or Government Gateway login fast.
Appeal if you have a reasonable excuse — but file and pay first.
Triage if you’ve missed multiple deadlines: file → pay what you can → Time to Pay → appeal → amend for missed reliefs.
Don’t freeze. The penalties get worse every day you wait.

For the full MTD deadline calendar, see our MTD quarterly updates guide. For the complete penalty ladder with worked examples, see our Self Assessment penalties guide. For estimating your penalty, use our penalty calculator.

Back to Panic Room · Back to Guide