The Construction Industry Scheme (CIS) is a cornerstone of tax compliance for contractors in the UK. When HM Revenue & Customs (HMRC) issues penalties under CIS, for late returns, incorrect filing, or other compliance failures, it’s crucial to understand how those penalties arise, what rights you have to appeal them, and how future compliance changes (like right to work checks or Making Tax Digital) could increase the stakes.

This guide breaks down:

• The key types of CIS penalties contractors face
• How and when you can appeal a CIS penalty
• What “reasonable excuse” means in practice
• The relationship between penalties and future compliance obligations
  
  

Why HMRC Issues CIS Penalties

Contractors must operate the CIS correctly every month. This means:

• Registering for CIS
• Verifying subcontractors with HMRC
• Making the correct tax deductions
• Filing monthly CIS returns on time, even if no subcontractors were paid
• Paying amounts deducted to HMRC by their due dates

Failing any of these obligations can trigger a penalty. Because CIS operates on monthly cycles, penalties can be frequent and significant, especially if left unchallenged.

Main Categories of CIS Penalties and Grounds for Appeal

1. Late Filing Penalties

One of the most common penalties contractors receive is for late submission of monthly CIS returns. According to HMRC:

• £100 if a return is late by one day
• £200 if it’s two months late
• £300 or 5% of the CIS deductions shown on the return (whichever is higher) if six months late
• A further £300 or 5% penalty at 12 months late
• After 12 months, penalties can go up to £3,000 or 100% of the CIS deductions amount if HMRC considers the circumstances deliberate or concealed.

These penalties are automatically charged by HMRC, so contractors often don’t even get a reminder before the penalties start.

Appealing a late filing penalty is established practice, you have the right to appeal if you disagree with the penalty notice. HMRC’s guidance says you must appeal within 30 days of the penalty being issued.

👉 Read this article for more information specifically on CIS late filing penalties and the critical timelines and strategy needed for avoiding late filing penalties in the future.

2. Incorrect Returns or Reporting Errors

Penalties also apply if a CIS return contains incorrect information. For example:

• Wrong subcontractor verification details
• Incorrect calculation of deductions
• Mistakes in employment status reporting

In some cases, an incorrect declaration can lead to penalties of up to £3,000 if negligent.

Late filing is automatic; errors in returns can trigger probes by HMRC and may lead to compliance checks, which in turn can result in assessments for underreported deductions and associated penalties.

3. Failing to Verify Subcontractors

Before making a CIS payment to a subcontractor, contractors must verify them with HMRC so the correct deduction rate is applied.

Failing to verify subcontractors or applying the wrong deduction rate because verification wasn’t properly carried out can lead to penalties or disputes with HMRC over tax liability.

These types of penalties aren’t always automatic; often they arise as part of a compliance check or assessment process.

4. Other Penalties: Records and Declarations

Other possible penalties under CIS (beyond late filing and errors) include:

• Failing to provide required payment and deduction statements to subcontractors within 14 days
• Inaccurate statements given to subcontractors
• Failing to declare there are no employment contracts where applicable

These penalties often start with a fixed amount and can be followed by daily penalties depending on how long they persist.

Understanding CIS Penalty Appeals

If you disagree with a CIS penalty, whether for late filing, an incorrect return, or another compliance issue, you generally have 30 days from the date on the penalty notice to appeal directly to HMRC.

How to Appeal

According to HMRC:

• You can appeal online through HMRC’s online services or the Penalty Appeal Service (PAS) in your CIS online account.
• If you can’t use online services, you can appeal in writing, quoting your Unique Taxpayer Reference (UTR) and payment reference from the notice.

Once an appeal is lodged, HMRC will review it and either:

• Accept it and withdraw the penalty
• Reject it and provide a notice of outcome
• Offer an internal review if you’re dissatisfied
• And ultimately, if needed, you can take it to a tribunal if HMRC rejects your appeal, provided you have already made the initial appeal.
  
  

What Counts as a ‘Reasonable Excuse’?

HMRC won’t cancel a penalty just because you say you made a mistake. There must be a reasonable excuse, for example:

• Severe illness
• A fire or natural disaster
• System failures outside your control (e.g. HMRC online services outages)

HMRC evaluates the specific circumstances. The fact you were “too busy” or “forgot” is typically not considered a reasonable excuse. The burden is on you to provide supporting evidence. Guidance on this approach is implicit in HMRC’s appeal framework.

What Happens After You Appeal

Once HMRC receives your appeal:

• You’ll usually get an acknowledgement if submitted online
• They will then assess the appeal based on the evidence
• If the appeal is successful, HMRC will cancel or reduce the penalty and may refund any amount already paid
• If HMRC rejects your appeal, you can ask for an internal review or move to an independent tribunal, but only if the initial appeal has already been made and the internal review has not yet started.

Recent reporting indicates that as of 2025, a significant proportion of taxpayers succeed in appealing automated HMRC penalties, underscoring the value of challenging penalties when justified.

Other CIS Penalty Risks and Future-Facing Issues

Right to Work Checks

Although Right to Work Checks are not currently embedded in the statutory CIS penalty regime itself, expanded enforcement activity around employment eligibility can interact with CIS compliance where worker status is in question.

If HMRC considers a worker to have been misclassified due to a failure of right to work processes, this could inform broader compliance assessments, potentially resulting in adjustment notices or redirected penalties under PAYE or other tax mechanisms in the future.

Right to work check penalties themselves come from the Home Office, not HMRC, but both can affect a contractor’s tax and compliance position.

Making Tax Digital (MTD)

HMRC continues to expand Making Tax Digital requirements for various taxes. While CIS returns themselves are not yet subject to MTD for Income Tax, contractors should be alert for future developments that may bring CIS reporting into the MTD compliance net.

Where MTD policies apply (e.g. to VAT), non-compliance can lead to additional penalties and interact with CIS compliance obligations if records are poorly kept.

Practical Tips for Contractors Facing CIS Penalties

• Act within 30 days of receiving a penalty notice to preserve your right to appeal.
• Gather evidence supporting your reasonable excuse before submitting the appeal.
• File late returns promptly even when appealing, this often reduces further penalties.
• Use HMRC’s online Penalty Appeal Service (PAS) where possible for faster processing.
• Keep records of all CIS paperwork and correspondence with HMRC for at least several years.

CIS penalties can have a material impact on contractors’ finances and cash flow. Thankfully, HMRC’s rules are clear: you have an established right to appeal penalties within a defined timeframe, and many penalties can be successfully challenged if supported by evidence and valid reasoning.

Staying on top of monthly returns, understanding what triggers penalties, and being proactive about appeals will give contractors the best chance of reducing liability and managing compliance risk effectively. 

If you want help staying on top of CIS compliance and filing or if you need help appealing a CIS penalty give Hudson Contract a call today.