Self-Assessment Penalties: How They're Calculated And How To Challenge Them

You owe HMRC no tax—but you've just received penalty notices totalling £1,600. That's not a typo. Self Assessment late filing penalties can stack up to £1,600 even when your tax bill is zero, because the penalties are for not filing, not for owing money.

If you haven't yet filed the return, do that first—even if you plan to appeal the penalties. Filing stops the daily penalties from accruing and prevents the higher 6-month and 12-month penalties from being triggered.

This guide walks you through exactly how the penalties are calculated, how to check whether HMRC got it right, and the three practical routes for challenging them: proving a reasonable excuse, getting the notice to file withdrawn, or showing that HMRC made a procedural error. For a broader overview of all penalty regimes, see our general penalties guide.

Note: From April 2026, taxpayers with business or property income over £50,000 move to a new points-based penalty regime as part of Making Tax Digital. The penalties described in this guide (Schedules 55 and 56 FA 2009) continue to apply to anyone not yet mandated into the new system.

How SA Penalties Stack Up

Self Assessment has two separate penalty regimes that run in parallel: late filing penalties and late payment penalties. If you filed late and paid late, you can be hit with both.

Late Filing Penalties (Schedule 55)

Schedule 55 of the Finance Act 2009 sets out penalties that escalate the longer you go without filing. They apply from the day after your filing deadline—31 January for electronic returns, 31 October for paper returns.

The "minimum cumulative" column shows what you'd owe if no tax is due—the £300 floor applies at 6 and 12 months regardless. If you do owe tax above £6,000, those penalties are 5% each, so the total is £1,000 plus 10% of your tax liability. On a £50,000 tax bill, that's £6,000 in filing penalties alone.

The £100 initial penalty is automatic. It applies whether you owe £50,000 or nothing at all.

Worked example 1: No tax owed, 14 months late. You were required to file a 2023–24 return by 31 January 2025 but didn't file until April 2026—14 months late. Your tax liability is £0.

• 1 day late (1 Feb 2025): £100
• 3 months late (1 May 2025): £10/day x 90 days = £900
• 6 months late (1 Aug 2025): greater of 5% of £0 (= £0) or £300 = £300
• 12 months late (1 Feb 2026): greater of 5% of £0 (= £0) or £300 = £300
• Total: £1,600—for a return showing zero tax.

Worked example 2: £5,000 tax owed, 14 months late. Same timeline, but this time your return shows £5,000 of tax due.

• 1 day late: £100
• 3 months late: £900
• 6 months late: greater of 5% of £5,000 (= £250) or £300 = £300
• 12 months late: greater of 5% of £5,000 (= £250) or £300 = £300
• Total: £1,600

The penalties are the same in both examples because 5% of £5,000 is less than £300. The tax-geared element (the part calculated as a percentage of your tax bill) only exceeds the £300 minimum when your tax liability is above £6,000.

Worked example 3: £20,000 tax owed, 14 months late. Now the 5% bites.

• 1 day late: £100
• 3 months late: £900
• 6 months late: 5% of £20,000 = £1,000
• 12 months late: 5% of £20,000 = £1,000
• Total: £3,000—nearly double the zero-tax scenario, plus you'd face separate late payment penalties and interest on the £20,000.

For deliberate withholding of information, the 12-month penalty can reach 70% of the tax liability (deliberate but not concealed) or 100% (deliberate and concealed) under paragraphs 6(2)–6(4) of Schedule 55. These higher rates are rare in practice—most late filing is non-deliberate.

Late Payment Penalties (Schedule 56)

Schedule 56 of the Finance Act 2009 applies separately if you don't pay the tax you owe by the due date (31 January). These penalties are proportional to your unpaid tax—if you owe nothing, there are no late payment penalties.

The maximum cumulative penalty is 15% of the unpaid amount.

Worked example: £5,000 unpaid for 14 months.

• 30 days late (2 March 2025): 5% of £5,000 = £250
• 6 months late (1 August 2025): 5% of £5,000 = £250
• 12 months late (1 February 2026): 5% of £5,000 = £250
• Total late payment penalties: £750

On top of this, you'd owe interest on the £5,000 (see the Interest On Late Payment section below).

If you make payments on account (advance payments due on 31 January and 31 July each year), late payment penalties apply to those separately. The same 5% surcharges are triggered if a payment on account remains unpaid 30 days, 6 months, or 12 months after its due date.

Late Filing And Late Payment Together

If you filed late and paid late, you get both sets. With £5,000 tax owed and 14 months late on both, you'd face £1,600 in filing penalties plus £750 in payment penalties—£2,350 before interest. And these are per year. Miss multiple years and the penalties multiply accordingly.

How To Check HMRC's Calculation

Before deciding how to challenge your penalties, check whether HMRC has calculated them correctly. Errors are not uncommon.

Was The Notice To File Validly Issued?

The filing obligation arises when HMRC issues you a notice to file under section 8 of the Taxes Management Act 1970—not from having income or owing tax. If HMRC never validly issued a notice, no filing obligation arose and no penalties can follow.

Did you receive the notice? Was it sent to the right address? In HMRC v Hansard [2019] UKUT 391 (TCC), the Upper Tribunal cancelled penalties where notices were addressed to an incomplete address. If you use HMRC's Personal Tax Account (PTA), the notice may have been sent electronically—in Cruise v HMRC [2023] UKFTT 41 (TC), the tribunal confirmed electronic PTA notifications satisfy the statutory requirement.

When Was Your Return Filed?

Check the exact date HMRC recorded your return as received. If you filed online, you should have received a 16-digit confirmation code—this is your proof of submission. If you didn't get one, the return may not have been successfully submitted. If HMRC has the wrong filing date, the penalties could be higher than they should be.

Were Daily Penalty Notices Properly Served?

The £10-per-day penalty (up to £900) requires HMRC to give you a specific notice under paragraph 4(1)(c) of Schedule 55. HMRC typically sends SA Reminder and SA 326D notices for this purpose, and the Court of Appeal confirmed in Donaldson v HMRC [2016] EWCA Civ 761 that HMRC's general policy decision to charge daily penalties is sufficient—no individual decision about each taxpayer is required.

But if HMRC cannot prove they sent the notice, the daily penalties may be invalid. In Hogg v HMRC [2017] UKFTT 538 (TC), the tribunal cancelled daily penalties of £580 and £820 where HMRC couldn't evidence that an SA Reminder or SA 326D had been sent.

Were Tax-Geared Penalties Correctly Calculated?

The 6-month and 12-month penalties are each 5% of your tax liability, with a £300 minimum. If HMRC assessed these before you filed, they should have charged the £300 minimum.

Once you file, paragraph 24(2)(b) of Schedule 55 requires HMRC to reassess based on the actual tax shown. If your liability is zero, both penalties should be £300 each. Check that HMRC has reassessed correctly.

Was The Penalty Notice Sent To The Right Address?

Penalty notices must be properly served. If HMRC sent them to the wrong address, this may be relevant to your appeal. In Hansard, the Upper Tribunal cancelled penalties where notices were addressed to an incomplete address ("Lot 2" only).

"I Never Needed To File"—The Section 8B Route

If you were wrongly brought into Self Assessment—perhaps because of an accidental registration, an employer error, or a situation that changed—there's a specific route for getting out.

Who Can Use This

Section 8B of the Taxes Management Act 1970 allows HMRC to withdraw a notice to file. This is relevant if you were registered for SA but shouldn't have been—for example:

• Your only income was PAYE salary taxed at the correct rate
• You were registered because of the High Income Child Benefit Charge but your adjusted net income was actually below £60,000
• You registered as self-employed but never started trading
• An employer mistakenly registered you
• Your circumstances changed and you no longer met the SA criteria

You cannot use this route if you've already filed a return for that year, or if HMRC has made a determination under section 28C.

How To Request Withdrawal

Contact HMRC's Self Assessment helpline (0300 200 3310) or write to the address on your penalty notice. Explain why you should not have been required to file and ask them to withdraw the notice under section 8B. Be specific about why you didn't meet the SA criteria.

Time Limit

HMRC can only withdraw the notice within the "withdrawal period"—two years from the end of the tax year in question (section 8B(6)). For the 2023–24 tax year, that means the deadline is 5 April 2026. After that, withdrawal is only possible in exceptional circumstances.

Penalty Cancellation Under Paragraph 17A

Here's the important part: when HMRC withdraws a notice to file, paragraph 17A of Schedule 55 allows them to cancel all associated late filing penalties. The withdrawal notice may include cancellation of penalty liability—in practice, HMRC generally cancels the penalties if it accepts you never needed to file.

In Berthet v HMRC [2017] UKFTT 694 (TC), a French lawyer was registered for SA prematurely despite having no UK income. The tribunal found HMRC's decision not to reduce her daily penalties was "flawed" because HMRC had failed to consider using section 8B to withdraw the notice and cancel penalties under paragraph 17A. The tribunal held that HMRC should have told her about the withdrawal option when she contacted them.

If HMRC refuses to withdraw the notice or refuses to cancel penalties after withdrawal, you can appeal that decision.

The Paperless Communications Trap

This is one of the most common reasons people accumulate large SA penalties without knowing.

When you interact with HMRC online—filing a return, checking your tax code, or using any HMRC digital service—you may inadvertently opt into "paperless" communications through HMRC's Personal Tax Account (PTA). Once opted in, HMRC sends your notices to file, penalty notices, and other correspondence to your PTA instead of by post. You'll receive a generic email telling you there's a new message in your PTA, but the email doesn't say what it's about.

Many people delete these emails as spam. If you don't check your PTA, you can go months or years without knowing that penalties are stacking up.

Two tribunal cases show how differently this plays out. In Howarth v HMRC [2025] UKFTT 499 (TC), Mrs Howarth had inadvertently opted into paperless communications during a prior return submission—without understanding what she was agreeing to. She treated HMRC's generic emails as spam and didn't learn of £1,600 in penalties until a debt collection letter arrived by post over a year later. The tribunal cancelled all penalties—she had no reason to know she'd opted in.

By contrast, in Cruise v HMRC [2023] UKFTT 41 (TC), Mr Cruise had actively signed up for online services. Not checking his PTA was not a reasonable excuse because he had voluntarily opted in. His £1,300 in penalties stood.

The distinction: inadvertent opt-in can support a reasonable excuse; active opt-in generally will not.

To check your settings, log into your Personal Tax Account and look at your communication preferences. You can switch back to paper at any time—but that won't undo penalties already charged.

Reasonable Excuse—SA-Specific Pitfalls

If you can show you had a "reasonable excuse" for filing or paying late, the penalty does not arise. This is the most common defence in SA penalty appeals, set out in paragraph 23 of Schedule 55 (filing) and paragraph 16 of Schedule 56 (payment).

For the full framework—including the four-step test tribunals use, what timeframes count as "without unreasonable delay", and detailed case examples—see our guide to reasonable excuse. Here we focus on the SA-specific traps that catch the most people.

The PTA Trap: Inadvertent Vs Active Opt-In

If your penalty notices went to HMRC's Personal Tax Account instead of by post, the outcome depends on how you were opted in. In Howarth v HMRC [2025] UKFTT 499 (TC), the taxpayer had inadvertently opted into paperless communications during a prior return submission—without understanding what she was agreeing to. All penalties cancelled. In Cruise v HMRC [2023] UKFTT 41 (TC), the taxpayer had actively signed up for online services and didn't check what his accountant was doing. His penalties stood. See The Paperless Communications Trap above for the full details.

"I Didn't Know I Had To File"

Not a reasonable excuse in itself. As the tribunal put it in Berthet v HMRC [2017] UKFTT 694 (TC), citing an earlier decision: "the Act does not provide shelter for mistakes, only for reasonable excuses." If you genuinely shouldn't have been in SA, use the section 8B route above instead—that's the correct mechanism for getting the notice withdrawn and the penalties cancelled.

"I Owe No Tax, So It's Disproportionate"

Not a ground of appeal. The penalty is for not filing, not for owing money. The tribunal has no power to reduce a penalty simply because it seems disproportionate to a nil tax liability.

How To Appeal

If you believe you have grounds—reasonable excuse, section 8B withdrawal, or a defect in HMRC's process—here's how to challenge your penalty.

The 30-Day Deadline

You have 30 days from the date of the penalty notice to appeal. This deadline applies whether you're appealing to HMRC or directly to the tribunal. Check the date on each penalty notice—if you've received multiple penalties at different times, each has its own deadline.

For more detail on appeal rights, see our guide to understanding your HMRC appeal rights.

Online Appeal Or SA370 By Post

You can appeal SA penalties either online or by post:

• Online: Use GOV.UK's interactive appeal tool, which walks you through the process.
• By post: Complete an SA370 form (for late filing penalties) or SA371 form (for late payment penalties) and send it to the address on your penalty notice. Both forms are available through the GOV.UK appeal guidance page.

Either way, you'll need to explain the grounds for your appeal—your reasonable excuse, the procedural error, or why you should not have been in SA.

What To Include

Your appeal needs to cover:

• Which penalties you're appealing—reference the penalty notice date and tax year
• Your grounds—reasonable excuse, procedural error, or section 8B
• A timeline of events with dates
• Supporting evidence—medical records, screenshots, correspondence with HMRC, or proof of address
• The outcome you want—cancellation, reassessment, or withdrawal of the notice to file

Request A Statutory Review First?

Before going to the tribunal, you can ask HMRC to review the decision. A different HMRC officer looks at your case independently and must complete the review within 45 days. It's free and doesn't prevent you from going to the tribunal afterwards—if the review doesn't resolve things, you have 30 days from the review conclusion letter to appeal to the tribunal.

If You've Missed The Deadline

If the 30 days deadline has passed, you can still apply for a late appeal. You'll need to explain the delay. In Howarth, the tribunal admitted late appeals (176 to 519 days late) because the delays were caused by the taxpayer being unaware of the PTA notifications—the same facts that supported the reasonable excuse.

Most SA penalty appeals fall into the Default Paper or Basic category at the tribunal. It costs £0 to appeal, and you generally won't face costs risk in these categories. For a step-by-step guide to the tribunal process, see how to appeal to the tax tribunal.

Special Reduction

Even if you can't show a reasonable excuse, HMRC has a discretionary power under paragraph 16 of Schedule 55 (and paragraph 9 of Schedule 56) to reduce a penalty because of "special circumstances."

The legislation explicitly excludes inability to pay as a special circumstance. Beyond that, HMRC is required to consider any unusual facts of your case. If HMRC refuses, the tribunal can review the decision—but applies judicial review principles, meaning it can only intervene if HMRC's decision was "flawed."

In both Berthet and Hogg, the tribunal found HMRC's refusal was flawed because they hadn't considered the section 8B withdrawal route. If HMRC fails to consider its own powers, its special reduction decision can be overturned.

Interest On Late Payment

Interest is separate from penalties. HMRC charges late payment interest on any unpaid tax from the original due date (31 January), accruing daily until payment. As of January 2026, the rate is 7.75% (Bank of England base rate plus 4%)—check HMRC's interest rates page for the current figure.

Interest cannot be appealed. For a full explanation of how interest is calculated, the April 2025 rate increase, and what you can do if you think HMRC got it wrong, see our interest on unpaid tax guide. If you can't pay in full, you can contact HMRC (0300 200 3820 for Self Assessment) to discuss a Time to Pay arrangement—entering one before the penalty trigger dates can also prevent late payment penalties from being charged. Interest continues to accrue during the arrangement, but HMRC will generally agree to a reasonable instalment plan.

If you have a live appeal against the penalties, HMRC will not normally pursue enforcement of those penalties while the appeal is being resolved. But the underlying tax and interest remain due. If you ignore both the penalties and the tax, HMRC can use debt collection agencies, take enforcement action through the courts, or—in some cases—recover the debt directly from your wages or bank account.

Key Legislation And Resources

Legislation:

• Section 8, Taxes Management Act 1970 — obligation to file when notice issued
• Section 8B, Taxes Management Act 1970 — withdrawal of notice to file
• Schedule 55, Finance Act 2009 — late filing penalties
• Schedule 56, Finance Act 2009 — late payment penalties

GOV.UK guidance:

• Self Assessment penalties — headline penalty amounts
• Estimate your Self Assessment penalties — interactive calculator
• Check when to appeal a Self Assessment penalty — step-by-step appeal guide
• HMRC interest rates — current rates for late payment and repayment interest

Key cases:

• Donaldson v HMRC [2016] EWCA Civ 761 — daily penalty requirements
• Perrin v HMRC [2018] UKUT 156 (TCC) — the four-step reasonable excuse test (see our case analysis)
• HMRC v Hansard [2019] UKUT 391 (TCC) — penalty notice service and address requirements
• Howarth v HMRC [2025] UKFTT 499 (TC) — inadvertent paperless opt-in and reasonable excuse

On this site:

• HMRC penalties explained — all penalty regimes overview
• What is a reasonable excuse? — the key defence
• How to appeal to the tax tribunal — step-by-step filing guide
• HMRC's internal review — the free review step
• Late appeal to the tax tribunal — missed the deadline?
• HMRC enquiries and closure notices — if penalties follow an enquiry
• Settling your tax tribunal case — settlement options once your appeal is filed
• Preparing for your tax tribunal hearing — if your appeal goes to a hearing
• After your tax tribunal decision — what happens next
• The tax dispute timeline — complete roadmap

This article is for informational purposes only and does not constitute legal or tax advice. For advice specific to your situation, consult a qualified tax adviser, accountant, or solicitor.