The 31 January 2026 deadline for filing your 2024/25 Self Assessment tax return has passed. Around one million people missed it, according to HMRC figures. If you are one of them, do not panic. The penalties start immediately, but acting quickly limits the damage.

HMRC issues automatic fines for late filing, even if you owe no tax or have already paid what is due. Interest and further penalties apply if tax remains unpaid. The sooner you file and pay, the less it costs overall.

Here is a straightforward breakdown of what happens and the practical steps to take right now.

The Penalties You Face for Late Filing

HMRC’s system triggers these automatically:

  • Immediate £100 fixed penalty (from day one late)
  • After 3 months (around 1 May 2026), daily penalties of £10 per day for up to 90 days (maximum £900)
  • After 6 months, a further penalty of 5% of the tax due or £300, whichever is greater
  • After 12 months, another 5% or £300, whichever is greater

These filing penalties build up regardless of your tax position. If you owe nothing, the £100 is often the main hit, but delays push costs higher.

Late Payment Penalties and Interest If Tax Is Owed

If you have a tax bill outstanding:

  • Interest runs at the current late payment rate (7.75% from January 2026) on any unpaid amount from 1 February onwards
  • 5% late payment penalty on unpaid tax after 30 days (around 2 March 2026)
  • Further 5% penalties at 6 months and 12 months late

Interest compounds daily, so paying soon stops it growing.

Note that Making Tax Digital changes start affecting some from April 2026, but for this 2024/25 return, the standard rules apply.

Step 1: File Your Return as Soon as Possible

Log into your Government Gateway account and submit online straight away. This stops daily penalties from starting or continuing.

Gather your records quickly: income, expenses, dividends, pensions, and any reliefs. Use HMRC’s online tool or compatible software to complete it.

If you use an accountant, contact them urgently to prioritise your return.

Filing now avoids the £10 daily charge that kicks in after three months.

Step 2: Pay Any Tax Owed Immediately

Pay what you can afford, even if not the full amount. This reduces interest and delays late payment penalties.

Use bank transfer, debit card, or set up a payment plan through HMRC if you cannot pay in full. Time to Pay arrangements are available for genuine hardship.

Contact HMRC via your online account or phone to discuss options before penalties escalate further.

Step 3: Check for Reasonable Excuse or Appeal

If you had a valid reason for the delay (serious illness, bereavement, or major disruption), you can appeal the penalties.

HMRC considers appeals case by case. Submit one online or in writing with evidence. They may cancel or reduce fines if your excuse holds.

Many appeals succeed for first-time issues with good reason.

Step 4: Get Organised to Avoid This Next Time

Use this as a chance to improve. Digital tools help track deadlines, store records, and monitor company details.

For limited company owners or those checking filings, quick access to Companies House information saves time on admin.

The Companies House on the Go app lets you search companies, view accounts, confirmation statements, and updates from your phone. It is simple and keeps you informed without full logins.

Download for iOS: https://apps.apple.com/us/app/uk-companies-house-on-the-go/id6743302358

Or Android: https://play.google.com/store/apps/details?id=com.companiesonthe.go

Explore more on efficient company management at Companies on the Go.