CIS tax return penalties: how much you could owe

What are CIS tax return penalties?

If a subcontractor’s Self Assessment return reporting CIS income is late, HMRC’s penalties start at £100 from day one, rising to £10 a day after three months (capped at £900), then a further £300 or 5% of the tax due at six and twelve months.

This is a different penalty system to the one HMRC charges contractors for late monthly CIS returns.

Subcontractors using Making Tax Digital for Income Tax follow a separate, points-based system instead. The sections below break down each of these in turn, along with how to appeal one.

Two different HMRC systems both get called CIS tax return penalties in everyday conversation, and mixing them up is an easy mistake to make.

One applies to contractors filing a monthly return; the other applies to subcontractors filing their annual Self Assessment return to reconcile the tax a contractor has already deducted from their pay.

This page is about the second one — the penalties that affect a subcontractor’s own tax return, not the monthly CIS300 return contractors file.

For everyone here because a Self Assessment deadline has been missed or is coming up, the sections below cover what income to include CIS tax return filers need to declare, how the penalties add up, how appeals work, and what changes under Making Tax Digital.

CIS tax return penalties: which system applies to you

HMRC runs two separate penalty regimes under the Construction Industry Scheme, and both get shortened to “CIS penalties” in everyday conversation.

Contractors file a monthly return (the CIS300) reporting payments made to subcontractors, and HMRC penalises a contractor separately if that return is late — a system with its own £100 fixed penalty, its own two-month step, and its own six and twelve-month charges.

Subcontractors don’t file that monthly return. Instead, a subcontractor reports CIS income through their annual Self Assessment tax return, reclaiming any tax the contractor already deducted. It’s this CIS self assessment penalty regime — the one triggered when a subcontractor’s own tax return is late — that the rest of this page covers.

Looking for the contractor side instead? GOV.UK’s guidance on filing monthly CIS returns sets out that regime in full.

The penalty ladder for a late CIS tax return

The penalties for late CIS tax return submissions follow the same ladder as any other Self Assessment return, because a subcontractor’s CIS income is reported through that same annual return. Some people refer to this as a CIS late tax return penalty, though HMRC’s own terminology is simply a late filing penalty for Self Assessment.

Miss the 31 January online deadline and HMRC applies penalties automatically, in this order:

• One day late: an immediate £100 penalty — the £100 penalty late tax return CIS filers face regardless of whether any tax is actually owed.
• Three months late: an additional £10 a day, for up to 90 days — up to £900 on top of the initial £100.
• Six months late: a further penalty of £300 or 5% of the tax due, whichever is higher.
• Twelve months late: another £300 or 5% charge, on top of everything already owed.

A subcontractor filing over 12 months late is looking at penalties of at least £1,600 before interest, even on a return with no tax owed.

This CIS subcontractor late filing penalty regime doesn’t distinguish between someone who owes nothing and someone with a large tax bill — the £100, £10-a-day and first £300 charges are fixed, and only the 5%-of-tax option changes depending on the size of the bill.

See GOV.UK’s Self Assessment penalties guidance for the full breakdown, including late-payment penalties on any tax owed.

Why the penalties escalate so quickly

HMRC’s filing penalties aren’t calculated on how much tax is owed — that’s the point of the early fixed stages.

The £100 charge exists to get the return filed at all; the daily penalties exist to stop three months turning into six, and six into twelve.

Only once a year has passed does the system start scaling with the size of the tax bill, and by then interest has usually been accruing on any unpaid tax separately from these filing penalties.

In practice, this means a small, straightforward return that’s a week late costs the same £100 as a much larger one that’s a week late — the escalation kicks in with time, not with the size of the refund or bill involved.

Can you appeal a CIS tax return penalty?

Yes — if there’s a reasonable excuse, HMRC will consider cancelling the penalty. Knowing how to appeal a CIS tax return penalty starts with the deadline: an appeal normally has to be lodged within 30 days of the date on the penalty notice, either online or in writing.

A CIS tax return penalty appeal reasonable excuse generally means something unexpected and outside your control got in the way of filing on time — a close bereavement, a serious illness or unexpected stay in hospital, a fire, flood or theft that destroyed records, or a documented failure in HMRC’s own online service.

Being busy, forgetting the deadline, or an accountant failing to file on your behalf are not usually accepted on their own.

HMRC won’t normally look at a CIS tax return late penalty appeal until the return itself has actually been submitted — filing first, then appealing, is the usual order. The same applies to a self assessment late penalty appeal generally: submit the outstanding return, then make the case for why it was late.

CIS penalty making tax digital: how it works

Making Tax Digital for Income Tax is changing how CIS penalty making tax digital works, but only for subcontractors who fall within it.

From 6 April 2026, sole traders and landlords with qualifying income above £50,000 must use Making Tax Digital for Income Tax, with the threshold dropping to £30,000 from April 2027 and £20,000 from April 2028.

Below that threshold, the standard penalty ladder above still applies in full.

For subcontractors who are brought in, the old fixed penalties are replaced by a CIS tax return penalty points system. Each missed submission — a quarterly update or the annual return — adds one point.

Reach the threshold (four points if you’re required to use Making Tax Digital, or two points if you’ve joined voluntarily) and HMRC charges a £200 penalty, with a further £200 for every late submission after that.

Points expire automatically after 24 months if you stay below the threshold; once you’re at the threshold, points only clear after a run of on-time submissions.

Late payment works differently again. There’s a short grace period (30 days in a subcontractor’s first year under the new rules, 15 days after that), and an HMRC CIS late payment penalty under this system is charged as a percentage of the tax outstanding, rising the longer it goes unpaid, then at an annual rate accruing daily until it’s settled.

The exact percentages have been revised more than once recently, so they’re worth checking directly on GOV.UK before relying on them.

How to avoid CIS tax return penalties

Most CIS tax return penalties are entirely avoidable, since they’re triggered by a missed deadline rather than an error in the figures.

A few habits make the biggest difference: file online rather than by paper, since the online deadline (31 January) is three months later than the paper one; register for Self Assessment well before the 5 October deadline in the year you need to; and if a payment can’t be made in full, contact HMRC about a Time to Pay arrangement before the deadline rather than after, since penalties can sometimes be avoided once an arrangement is agreed.

Keeping contractor payment and deduction statements together throughout the year, and using a CIS tax rebate calculator to keep track of what’s likely owed, also makes the return itself quicker to complete — which removes one of the most common reasons a return ends up filed at the last minute, or not at all.

Before you file next time

CIS tax return penalties apply to a subcontractor’s annual Self Assessment return, not the monthly return contractors file — and they start at £100 the moment the deadline passes, regardless of whether any tax is owed.

The ladder rises at three, six and twelve months, appeals are possible within 30 days if there’s a genuine reasonable excuse, and Making Tax Digital for Income Tax replaces the ladder with a points-based system for subcontractors who fall within it.

None of this affects a subcontractor’s right to reclaim CIS deductions already paid — a penalty reduces what’s ultimately received, but the underlying refund is calculated separately.

The CIS tax refund guide covers how that reclaim process works in full.

Key takeaways

Here’s the short version, if you don’t read anything else on this page:

• A late CIS tax return picks up an automatic £100 penalty from day one, even if no tax is owed.
• Further penalties apply at three months (£10 a day, capped at £900), six months, and twelve months (£300 or 5% of the tax due each time).
• This is a different system to the one HMRC applies to contractors’ late monthly CIS returns.
• Appeals must normally be lodged within 30 days of the penalty notice, and need a genuine reasonable excuse.
• Making Tax Digital for Income Tax replaces this ladder with a points-based penalty system for subcontractors who fall within its income thresholds.
• A penalty doesn’t cancel a CIS tax refund — it’s deducted from what’s ultimately paid back.

Common CIS tax return penalty questions

The questions below cover situations GOV.UK guidance addresses but that the sections above don’t go into in full.

What counts as a reasonable excuse for a late CIS tax return?

HMRC generally accepts a reasonable excuse where something unexpected and outside a subcontractor’s control prevented the return being filed on time. Examples include a partner or close relative dying shortly before the deadline, an unexpected stay in hospital, a fire, flood or theft that destroyed the records needed to complete the return, or a documented failure in HMRC’s own online filing service.

Being busy, forgetting the deadline, or relying on someone else — such as an accountant — who then failed to file are generally not accepted on their own. HMRC also expects the return to be filed as soon as possible once the excuse no longer applies; continuing to cite an excuse long after it’s resolved is less likely to succeed.

Does a contractor’s late CIS return affect a subcontractor’s own penalty or refund?

Not directly. A contractor’s monthly CIS return and a subcontractor’s Self Assessment return are two separate filing obligations, each with its own penalty regime, and one being late doesn’t automatically create a penalty on the other.

Where it can cause a practical problem is the CIS deductions themselves: if a contractor’s monthly return is late or missing, the deductions taken from a subcontractor’s pay may not show up correctly on that subcontractor’s HMRC record, which can delay matters even though the subcontractor’s own return was filed on time. A CIS tax refund after penalty amounts (if any) have been settled is still paid out in full for whatever balance remains owed, once everything is reconciled — checking payment and deduction statements against HMRC’s online record is the most reliable way to catch discrepancies early.

Can you use a CIS tax return penalty calculator to check what’s owed?

HMRC provides an online tool to estimate Self Assessment penalties, which covers the same fixed and daily penalties that apply to a subcontractor’s CIS tax return. It asks for the filing deadline and the date the return was (or will be) submitted, then works out the penalty due at each stage.

It’s an estimate rather than a final figure, since HMRC’s own systems calculate the actual amount charged, but it’s useful for getting a realistic sense of how quickly the total is likely to grow the longer a return is left outstanding.

What happens if a CIS tax return penalty can’t be paid straight away?

A penalty that isn’t paid on time attracts interest in the same way unpaid tax does, on top of the penalty itself. Contacting HMRC before the payment deadline to discuss a Time to Pay arrangement is generally the better route than missing the deadline and hoping to sort it out afterwards, since an agreed arrangement that’s kept to can sometimes avoid further penalties being added.

Ignoring an outstanding penalty doesn’t make it disappear — HMRC can pursue the debt in the same way as unpaid tax, and interest continues to accrue on the outstanding balance until it’s settled in full.

How long should CIS tax return records be kept, and could missing records trigger a check?

HMRC’s general rule for how long to keep CIS tax return records is at least five years after the 31 January submission deadline for the tax year in question, covering invoices, payment and deduction statements, and any other evidence used to complete the return.

HMRC accepts digital receipts CIS tax return filers submit as evidence, provided they’re kept in a format that can be produced if requested — a scanned copy or a securely stored photo is generally sufficient. Gaps or inconsistencies in these records are one of the things that can prompt HMRC to open a wider compliance check, so keeping them organised is worth doing even though it isn’t itself a penalty-generating deadline.