Self Assessment • VAT • Corporation Tax

Your complete guide to understanding HMRC charges and how to avoid them

HMRC has wide-ranging powers to impose financial penalties on individuals and businesses that fail to meet their tax obligations. Whether it is a late return, an unpaid tax bill, or an error on a submission, the charges can add up quickly in some cases reaching 100% of the tax originally owed.

This guide breaks down the penalty regimes across the three most common tax types, so you know exactly what you are facing and more importantly how to stay on the right side of HMRC.

Key rate to know: HMRC’s late payment interest rate is currently 7.75% per annum (Bank of England base rate + 4%), as of May 2026. This applies across Self Assessment, VAT, and Corporation Tax.

1. Self Assessment Penalties

Self Assessment applies to individuals, sole traders, and partners in partnerships. Penalties fall into two main categories: late filing and late payment.

Late Filing Penalties

Missing the Self Assessment filing deadline 31st January for online returns triggers an automatic escalating penalty structure:

• 1 day late: An immediate £100 fixed penalty applies automatically, even if no tax is owed or you are due a refund.
• 3 months late: Daily penalties of £10 per day begin to accrue, up to a maximum of 90 days (£900).
• 6 months late: A further charge of the greater of £300 or 5% of the tax due is added on top of earlier penalties.
• 12 months late: An additional £300 or 5% of tax due applies. In the most serious cases – where HMRC believes information has been deliberately withheld – this can rise to 100% of the tax due.

Important: the £100 penalty applies regardless of whether you owe any tax. Filing on time is always worthwhile, even if payment is not immediately possible.

Late Payment Penalties

Separate from filing penalties, late payment of Self Assessment tax attracts both interest and percentage surcharges on the unpaid amount:

• Interest accrues from the payment deadline at the HMRC late payment rate (7.75% per annum as at May 2026).
• A 5% surcharge is added if the tax remains unpaid after 30 days.
• A further 5% surcharge is applied at 6 months late.
• An additional 5% surcharge is applied at 12 months late.

Tip: if you cannot pay your tax bill in full, file your return on time anyway. This avoids the late filing penalty entirely. You can then contact HMRC to set up a Time to Pay arrangement.

2. VAT Penalties

VAT penalties underwent significant reform from January 2023, with the new regime fully in effect by 2025. HMRC replaced the old default surcharge system with two separate penalty structures: one for late submission and one for late payment.

Late Submission: Points-Based System

HMRC now operates a points-based system for late VAT returns, similar in concept to driving licence penalty points:

• Each late return earns 1 penalty point on your record.
• Quarterly filers reach the penalty threshold at 4 points, triggering a £200 charge.
• Monthly filers reach the threshold at 5 points.
• Annual filers reach the threshold at 2 points.
• Points expire after a period of good compliance and can be reset if HMRC’s conditions are met.

Why the change? The old default surcharge system was criticised as disproportionate for businesses that were occasionally late by small amounts. The points-based approach is designed to be fairer for genuine slip-ups while still penalising persistent non-compliance.

Late Payment: New Regime from April 2025

For VAT payments due on or after 1 April 2025, a revised late payment penalty structure applies:

• 0–15 days late: No penalty if the VAT is paid in full within 15 days of the due date.
• 16–30 days late: A first penalty of 2% of the VAT outstanding at day 15 is charged.
• 31 or more days late: A second penalty is added, calculated as 2% of the VAT outstanding at day 15 plus 2% of the VAT outstanding at day 30.
• Ongoing daily charge: From day 31, an additional daily penalty accrues at an annual rate of 4% of the outstanding balance.

In addition to these penalties, interest continues to accrue on unpaid VAT at the HMRC late payment rate from the date the VAT originally became due.

3. Corporation Tax Penalties

Corporation Tax applies to limited companies and certain other incorporated entities. The penalty regime differs somewhat from Self Assessment.

Late Filing Penalties

Corporation Tax returns (CT600) must be filed within 12 months of the end of the accounting period. Late filing penalties escalate as follows:

• 1 day late: £100 fixed penalty.
• 3 months late: An additional £100 fixed penalty.
• 6 months late: A further penalty of 10% of any unpaid Corporation Tax.
• 12 months late: A further 10% of any unpaid tax, bringing the total percentage charge to 20% for returns more than 12 months overdue.

Late Payment – Interest

Unlike Self Assessment, Corporation Tax does not carry fixed surcharges for late payment in the same way. Instead, interest is charged on unpaid tax at the HMRC rate, which for Corporation Tax is the Bank of England base rate plus 1%.

Large companies that pay tax by instalments may also face interest on underpaid instalments, calculated separately under a different rate.

4. Penalties for Inaccuracies – All Tax Types

Across all three tax regimes, HMRC has the power to charge penalties where returns or documents contain inaccuracies that lead to an understatement of tax. The penalty percentage depends on the behaviour behind the error:

• Careless errors (0%–30% of tax owed): Where reasonable care was not taken but there was no intention to mislead.
• Deliberate errors, not concealed (20%–70% of tax owed): Where you knew the return was wrong but did not actively try to hide it.
• Deliberate and concealed errors (30%–100% of tax owed): Where you knew the return was wrong and took active steps to conceal the inaccuracy from HMRC.

Reduction for disclosure: penalties can be significantly reduced if you voluntarily disclose an inaccuracy to HMRC before they discover it themselves. Unprompted disclosures attract lower penalties than prompted ones. In some careless error cases, the penalty can be reduced to nil.

5. HMRC Interest Rates

HMRC charges interest separately from penalties. Interest is not a penalty as such – it compensates HMRC for the late receipt of tax that was due. The key rates to be aware of are:

• Late payment interest: 7.75% per annum (Bank of England base rate + 4%), as of May 2026. This applies across Self Assessment, VAT, and Corporation Tax
• Repayment interest: Where HMRC owes you a refund, interest is paid at a lower rate (base rate + 0.5%, subject to a 0.5% minimum).
• Corporation Tax underpayments: Interest is charged at base rate + 1%.
• Rates change: HMRC interest rates track the Bank of England base rate and are reviewed regularly. Always check the current figures before making financial decisions.

For current rates, visit: gov.uk/government/publications/rates-and-allowances-hmrc-interest-rates-for-late-and-early-payments

6. How to Avoid Penalties

The good news is that most HMRC penalties are entirely avoidable with the right habits and professional support. Here are the key steps:

File on time, always

Even if you cannot pay your tax bill, filing your return by the deadline avoids the late filing penalty. The two charges are calculated independently – you will not be penalised for filing if payment is genuinely not yet possible.

Know your key deadlines

• 31 January – Self Assessment return and balancing payment deadline (online).
• 1 month and 7 days after VAT period end – VAT return submission and payment.
• 12 months after the end of the accounting period – Corporation Tax return (CT600).
• 9 months and 1 day after the end of the accounting period – Corporation Tax payment (for most small companies).

Use Time to Pay if you cannot pay

If you know you cannot pay your tax bill in full by the deadline, contact HMRC proactively before that date to arrange a Time to Pay (TTP) instalment plan. Interest will continue to accrue, but a TTP agreement can prevent escalating surcharges and demonstrate good faith.

Check your returns carefully

Careless errors can result in penalties of up to 30% of the tax due. Taking the time to review your figures thoroughly – or working with a qualified accountant – significantly reduces this risk.

Disclose errors promptly

If you discover a mistake in a return you have already submitted, tell HMRC as soon as possible. Voluntary, unprompted disclosure attracts substantially lower penalties than waiting for HMRC to identify the problem themselves.

Quick Reference Summary

Here is a brief overview of the day-one late filing penalties, late payment consequences, and inaccuracy penalty ranges across each tax type:Self Assessment

• £100 immediate fixed penalty for a return filed 1 day late.
• Daily £10 penalties from 3 months; 5% surcharges on unpaid tax at 6 and 12 months.
• Interest on unpaid tax plus 5% surcharges at 30 days, 6 months, and 12 months late.
• Inaccuracy penalties: 0% to 100% of tax owed, depending on behaviour.

VAT

• £200 fixed penalty once the points threshold is reached (e.g. 4 points for quarterly filers).
• No penalty if paid within 15 days; 2% to 4% fixed penalties plus a 4% annual daily rate from day 31.
• Inaccuracy penalties: 0% to 100% of tax owed, depending on behaviour.

Corporation Tax

• £100 immediate fixed penalty for a return filed 1 day late, rising to £200 at 3 months.
• 10% of unpaid tax at 6 months; 20% total at 12 months.
• Interest on late payments at Bank of England base rate + 1%.
• Inaccuracy penalties: 0% to 100% of tax owed, depending on behaviour.

Important Notice

This guide is for general information purposes only and reflects HMRC rules as understood in may 2026. Tax legislation and HMRC interest rates change regularly. You should not rely solely on this guide for decisions about your tax affairs. Please consult a qualified accountant or tax adviser for advice tailored to your specific circumstances.

Useful resources: gov.uk/self-assessment-tax-returns/penalties  •  gov.uk/guidance/how-late-payment-penalties-work-if-you-pay-vat-late  •  gov.uk/guidance/corporation-tax-penalties

I am your local accountant, the sole Director of the practice and my name is Sonya Jolly.

I qualified as a chartered certified accountant in 2000 and have over 20 years of general practice experience.

I have always worked with small owner-managed businesses and individuals. 

I feel my approach allows me to develop lasting relationships with clients, providing them with all their accountancy and taxation needs and requirements.

I like to get to know my clients well and to take the time to learn about all areas of their businesses, resulting in more tailored taxation and financial advice.

I am your local accountant, the sole Director of the practice and my name is Sonya Jolly.

I qualified as a chartered certified accountant in 2000 and have over 20 years of general practice experience.

I have always worked with small owner-managed businesses and individuals. 

I feel my approach allows me to develop lasting relationships with clients, providing them with all their accountancy and taxation needs and requirements.

I like to get to know my clients well and to take the time to learn about all areas of their businesses, resulting in more tailored taxation and financial advice.