Why a missed January deadline keeps growing

Figures relate to tax year 2025-26 (UK)

A British return is due at the end of January, and plenty of Americans here miss it. Usually because they were waiting on something American.

The first penalty is a hundred pounds and it arrives whether or not you owe any tax at all.

Then it grows, in steps, on a schedule most people have never seen set out.

Key takeaways

• A day late costs £100, even with no tax owed.
• Daily charges of £10 start after three months.
• Six and twelve month points add further charges.
• Late payment penalties run separately from late filing ones.
• Interest runs on the tax as well as the penalties.
• A reasonable excuse can get them cancelled.
• Americans miss the date waiting on US paperwork.
• Filing a provisional figure beats filing nothing.

What does late filing cost on day one?

A hundred pounds, immediately. According to GOV.UK guidance on Self Assessment penalties, the fixed charge applies the moment the deadline passes, whatever your tax position. Somebody due a refund still pays it, which strikes most people as harsh and is entirely settled.

Our guide to registering for Self Assessment covers the filing itself.

Nothing about owing nothing excuses the return.

What does late filing cost after three months?

Daily penalties begin, at ten pounds a day for up to ninety days. That adds as much as nine hundred pounds on top of the original charge, so a return still outstanding in the spring has already cost four figures. The daily clock is what does the damage.

Three months from the deadline falls at the end of April.

Most people have no idea this stage exists.

What does late filing cost after a year?

Each adds a further charge: the greater of three hundred pounds or five per cent of the tax due. So two more fixed points arrive, one in the summer and one the next winter. On a large bill the five per cent bites much harder than the floor.

Our guide to payments on account covers the tax itself.

A year late on a big bill is genuinely expensive.

How the charges stack up

Are late payment penalties separate?

Yes, entirely, and people conflate the two constantly. Paying late brings its own charges at thirty days, six months and twelve months, calculated on the outstanding tax. You can file on time and still collect payment penalties, or the reverse.

Our guide to an offer in compromise covers settling a debt in America.

Two regimes, two sets of letters.

Does interest run as well?

On the tax from the due date, and on unpaid penalties too. Interest is not a penalty and cannot be appealed on reasonable excuse grounds, so it accrues regardless of why you were late. It is the one charge nobody escapes.

Our guide to paying tax owed on a streamlined filing covers interest generally.

Paying the tax early stops the interest even if the return is late.

Why do Americans end up late filing?

Because they are waiting on something from the other side. A broker statement that lands in March, a partnership schedule that turns up in September, or an American return that has to be done first. Any of those can push a British filing well past January.

Our guide to US tax deadlines for expats covers the American dates.

In our practice this is the single commonest reason.

A worked example

Take an illustrative case. An American in London waits for an American statement before filing her British return.

It arrives in March, by which time the fixed penalty has landed.

She files in May, having collected the hundred pounds plus thirty days of daily charges.

Filing in January with a provisional figure and amending later would have cost her nothing at all.

Can you file a provisional figure?

You can, and far too few people do. Where a figure genuinely is not available, you enter your best estimate, tick the box saying it is provisional and amend when the real number arrives. The return counts as filed on time.

Our guide to exchange rates on a US return covers estimating figures.

Keep a note of how you arrived at the estimate.

What is a reasonable excuse?

Something outside your control that stopped you filing. HMRC publishes examples. Serious illness, a death in the family, a failure of its own service and postal strikes all count. Pressure of work and a missing adviser do not.

Our guide to reasonable cause relief covers the American equivalent.

You must also file without delay once the obstacle lifts.

Does waiting on US papers count?

On its own, not usually, which surprises people. HMRC expects a provisional figure instead, so the availability of the estimate defeats the excuse. Where a foreign source genuinely gave you nothing to estimate from, the argument is stronger.

Our guide to requesting a tax transcript covers getting American records.

Evidence of chasing the information helps a great deal.

How do you appeal a late filing penalty?

Within thirty days of the notice, online or by form. Set out the excuse and the dates. HMRC reviews it, and you can take it to the tribunal if refused. Most appeals that win do so on a clear list of dates rather than fine writing.

Our guide to first time penalty abatement covers the American parallel.

Appeal in writing even if you also telephone.

What if you did not owe a return?

Then ask HMRC to withdraw the notice to file. That cancels the penalty with it. Plenty of people stay registered for years after the reason ended, picking up charges for returns nobody needed. The request is free and it often works.

Our guide to moving back to the US covers leaving the system.

Deregistering properly prevents the whole problem.

Does a late filing penalty affect your US return?

Not as a credit, because a penalty is not a tax. The British tax itself still counts. The penalties and the interest on top do not. So a late British filing quietly costs money that nothing in America will give back.

Our guide to Form 1116 income baskets covers what counts.

Keep the penalty out of your creditable tax figure.

Does a paper return change the late filing date?

Yes, and it is three months earlier. Paper filings are due at the end of October while online ones run to the end of January, so somebody who posts a return in December is already late. Almost nobody abroad should be filing on paper.

Our guide to making tax digital covers the move online.

Register for online filing well before you need it.

How long does registration take?

Weeks rather than days, and longer from abroad because the activation code goes by post. Somebody who starts in January will not file in January. That delay is itself a common cause of a first year penalty.

Our guide to ITIN applications from the UK covers a similar wait.

Start the registration in the autumn.

Can penalties be reduced rather than cancelled?

The fixed charges are what they are, so it is mostly all or nothing. Behaviour-based penalties on an inaccurate return work differently, with reductions for disclosure and cooperation. The two regimes are often confused in the same letter.

Our guide to making a disclosure to HMRC covers inaccuracy penalties instead.

Read which penalty each line of the notice refers to.

What if you cannot pay the tax?

Ask for time to pay before the deadline rather than after it. An agreed arrangement stops the late payment penalties running, though interest continues. Asking early is treated very differently from going quiet and being chased.

Our guide to an IRS payment plan from abroad covers the American version.

The filing deadline and the payment deadline are the same day.

Do several late filing years compound?

Each year carries its own full set of charges, so three missed years produce three separate stacks. That is how a modest problem becomes a five figure one. Bringing the oldest year up to date first stops the daily clock soonest.

Our guide to streamlined eligibility covers the American catch-up.

File everything, then appeal across all the years together.

What records support a late filing appeal?

Dated evidence of what stopped you: medical letters, correspondence chasing a statement, screenshots of a failed service. Those prove the chronology, which is what the reviewer actually assesses. Assertions without dates rarely succeed.

Our guide to missing records in a streamlined filing covers rebuilding evidence.

Keep the envelope and the postmark where post is the issue.

When exactly is the deadline?

The thirty first of January following the end of the tax year, for both the return and the tax. So the year ending in April 2025 was due by 31 January 2026. The two obligations share a date, which is why people miss both at once.

Our guide to estimated tax payments from the UK covers the American rhythm.

Midnight means midnight, in UK time.

Does a partnership make it worse?

Considerably, because a late partnership return brings a penalty on every partner. One missed filing can therefore produce several hundred pounds of charges across a small firm. Partners rarely realise their own penalty came from somebody else's delay.

Our guide to a UK LLP and Form 8865 covers the American reporting.

The nominated partner holds the deadline for everybody.

What if HMRC sent the notice late?

Then you usually get three months from the date of the notice rather than the ordinary deadline. People registered for the first time partway through the year benefit from this most. Check the date on the notice before accepting a penalty.

Our guide to the statutory residence test covers why you registered.

A late notice is a genuine ground for cancellation.

Can an agent file for you?

Yes, once they are authorised, and authorisation itself takes weeks. The deadline belongs to you rather than to them, so an agent appointed in mid January will not save the date. Appoint one in the autumn if you intend to use one.

Our guide to choosing a US-UK tax accountant covers the appointment.

An agent's own delay is not a reasonable excuse for you.

Does HMRC chase you abroad?

The letters follow your address of record, and plenty never arrive. Penalties accrue whether or not you read the post, so an address left unchanged after a move is an expensive oversight. The online account shows everything regardless.

Our guide to UK bank account closures covers staying contactable.

Update HMRC separately from everybody else.

Is there a first offence concession?

Not a formal one, unlike the American system. HMRC looks at reasonable excuse rather than at your record, so a first lapse without a good reason is charged like any other. A long clean history helps the tone rather than the outcome.

Our guide to non-wilful conduct covers the American standard.

The two systems are less alike than they sound.

What if the return was wrong rather than late?

A different regime applies, based on behaviour and on whether you told HMRC yourself. Careless errors attract lower percentages than deliberate ones, and an unprompted disclosure reduces them further. Lateness and inaccuracy are judged separately.

Our guide to an HMRC enquiry covers what follows a wrong figure.

One return can attract both kinds of penalty.

Can you pay a penalty in instalments?

Often yes, on the same terms as the tax. HMRC will usually fold a penalty into a time to pay arrangement if you ask. Still, interest runs on it, so paying it off early is cheaper than spreading it over a year.

Ask for the tax and the penalty together, not separately.

One arrangement is simpler to keep track of.

Does an appeal pause the charge?

It usually suspends collection of the penalty while HMRC looks at it. But it does not suspend the tax, and it does not stop interest. So pay the tax, appeal the penalty, and let the two run on their own tracks.

Our guide to the accidental American covers a related position.

Never hold back tax because a penalty is disputed.

Does a penalty show on your record?

Not in any public way, and it affects no credit file. It sits on your HMRC record and nowhere else. So the cost is the money and the nuisance, rather than any lasting mark against your name.

Repeated lateness does colour how HMRC handles you later.

That is tone rather than a formal consequence.

How to deal with a late filing penalty

1. File the outstanding return immediately, estimating if you must.
2. Pay the tax even before the return is accepted, to stop interest.
3. Read the notice to see which penalties it actually charges.
4. Work out whether you had a reasonable excuse with dates.
5. Appeal within thirty days, in writing, with the chronology.
6. Ask HMRC to withdraw the notice if no return was ever due.
7. Agree time to pay if the tax itself is the problem.
8. Register for online filing in the autumn for next year.

Mistakes and penalties we see with late filing

The first is waiting for an American document instead of filing a provisional figure in January.

The second is assuming no tax due means no penalty, when the fixed charge ignores your liability entirely.

The third is staying registered for years after leaving Britain and collecting charges for returns nobody needed.

The fourth is claiming the penalties as creditable foreign tax on the American return, which they are not.

How US UK Tax Accountants helps

We file something in January, because a provisional figure costs nothing and a missed deadline starts a clock that runs for a year.

Then we appeal what can be appealed, with dates. Our UK Self Assessment service covers the return.

If penalty notices are stacking up, get in touch before the next stage lands.

Last reviewed 28 October 2026. This article is general information and not personal tax advice, and penalty figures change.