The full penalty picture and why April 2026 changed everything
The rules around CIS late filing got materially stricter from April 2026. Penalties that were once softened are now fully enforced, and they compound fast when you miss multiple months.
What changed in April 2026 and why it matters
Here’s the backstory, because it helps explain why this feels like a step change. Back in 2015, HMRC removed the requirement for contractors to file nil returns in months where they had no subcontractor payments. The problem was that without this requirement, contractors who went quiet for a few months would accumulate automatic late filing penalties for returns they didn’t even know they needed to file-the whole thing became a mess of appeals and cancelled penalties.
HMRC pragmatically suspended CIS late filing penalties other than the first fixed penalty of £100. From April 2026, with the nil filing requirement back in place, HMRC reinstated the full CIS late filing penalty regime. So the light-touch enforcement that’s been softening the impact of late filing for the last decade has ended. The full penalty structure, from £100 right up to tax-geared charges, is now live again.
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The new monthly obligation from April 2026 From April 2026, contractors are required by law to either file a CIS return every month, including nil returns in months where they have not used a subcontractor, or inform HMRC in advance that they will not pay subcontractors that month by submitting an inactivity request. There is no middle option. Failure to submit either a return or an inactivity notification will result in an automatic penalty. |
The filing deadline doesn’t change if the 19th falls on a weekend or bank holiday either. Monthly CIS returns are due by the 19th of the month following the tax month. The filing deadline of the 19th does not change for bank holidays or weekends-the return must be received by HMRC by the 19th regardless. Miss it by a day, and the penalty clock starts.
The full CIS penalty structure, step by step
The penalties follow a defined escalation path. Each monthly return is its own separate filing obligation. If you miss three monthly returns, you receive three separate £100 penalties totalling £300, not a single penalty. This is where people get the most unpleasant surprise. Here’s how it escalates per return.
Day 1
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1 day late First fixed penalty £100 Automatic. No discretion. No grace period. Even if no CIS deductions were due on that return, the penalty still applies. This is per return-missing three months costs £300 immediately. |
2 months
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2 months late Second fixed penalty + £200 A second automatic charge stacks on top of the £100. So a single return two months late has already cost £300 before any tax-geared element kicks in. |
6 months
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6 months late Tax-geared penalty first charge £300 or 5% of liability A tax-geared penalty at six months of a minimum of £300 or 5% of any liability which should have been shown on the return, whichever is higher. If your monthly CIS deductions are significant, 5% can be a considerable sum. |
12 months
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12 months late Tax-geared penalty second charge Up to 100% of liability The tax-geared element for returns over 12 months late depends on the nature of the failure, ranging from 5% for non-deliberate failures up to 100% for deliberate and concealed failures. A 100% penalty on a year’s CIS deductions is genuinely catastrophic. |
Daily
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6+ months late also possible Daily penalties £10/day (up to 90 days) Daily penalties of £10 per day can be charged after a return is 6 months late, up to 90 days, a maximum of £900. In practice, these are less commonly imposed than the fixed and percentage penalties, but they remain available to HMRC. |
“Miss six monthly returns for six months each, and before you’ve even looked at the tax-geared element, you’ve accumulated £1,800 in fixed penalties alone.”
The nil return trap everyone walks into
This is what most people miss, and it’s genuinely the most common source of CIS penalty calls we receive. In a quiet month, work dried up, a project finished, nothing to pay subcontractors the assumption is that there’s nothing to file. Wrong.
Failure to file a nil return triggers the same £100 penalty as a late return with data on it. Setting your CIS status to inactive with HMRC avoids the need to file nil returns each month. If you have no subcontractor payments for an extended period, contact HMRC to set your CIS contractor account to inactive. That inactivity status suspends the filing requirement for up to six months, which is genuinely useful for seasonal contractors.
Use the inactivity option use it
If you know you won’t be paying subcontractors for a while, notify HMRC in advance by submitting an inactivity request either through HMRC’s online service or by ticking the inactivity box on your next return. This suspends your filing obligation for up to six months without triggering penalties. When work picks up again, you simply reactivate. Don’t just go quiet. That’s the expensive option.
Example
A groundworks contractor came to us in early 2026, confused about a batch of penalty notices totalling nearly £1,400. He’d finished a major contract in November 2025 and didn’t start the next one until February 2026. Three quiet months. No subcontractors paid. No returns filed because, as far as he was concerned, there was nothing to report.
Under the old regime, those penalties would likely have been cancelled or reduced. Under the rules now in force from April 2026, they’re fully enforceable. We helped him appeal on the basis that the nil return requirement hadn’t been clearly communicated to him and HMRC accepted that argument for the pre-April months given the transitional nature of the change. But anything from April 2026 onwards? That defence doesn’t work anymore. The rules are published, the change was announced in the Autumn Budget 2025, and HMRC considers contractors to have had adequate notice.
When did you last check your CIS filing history? If there are any months where neither a return nor an inactivity notification was filed, you may already have penalties building.
Calculate your potential penalty exposure
Put in your numbers and see what the figures look like.
CIS Late Filing Penalty Estimator
Based on the full penalty structure reinstated from April 2026
Number of monthly CIS returns filed late………………………………………..3
How many months late is the latest return?…………………………………….2
Average monthly CIS deductions (£)……………………………………………..2000
Estimated exposure: £900
Fixed penalty per return……………………………………………………………….£300
Number of late returns…………………………………………………………………3
Total fixed penalties…………………………………………………………………….£900
Estimated total £900
This is an estimate using fixed penalty bands. Tax-geared penalties at 6 and 12 months vary by specific circumstances and HMRC discretion. Always get a professional view on your exact position.
Gross Payment Status-the consequence nobody talks about
If you or your business holds Gross Payment Status, meaning subcontractors can pay you in full without deducting CIS tax, late filing isn’t just a penalty issue. It puts that status at risk.
And from April 2026, the consequences of losing GPS have got significantly worse. Where Gross Payment Status is removed under these new powers, the waiting period before reapplying has increased significantly from one year to five years. Five years without GPS means five years of 20% deductions coming off every payment you receive. For a contractor with substantial turnover, that’s a serious cash flow hit sustained over an uncomfortably long period.
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New HMRC anti-fraud powers April 2026 HMRC has gained powers to immediately revoke Gross Payment Status where fraud is suspected, without waiting for a formal investigation. The reapplication waiting period has increased from one year to five years. Even where you weren’t directly involved in fraud, if HMRC determines you knew or should have known that a supply chain payment was connected to non-compliance, your GPS can be removed immediately. Due diligence on subcontractors isn’t optional anymore. It’s GPS protection. |
Can you appeal? Here’s what actually works
Yes, you can appeal, but the window is tight, and the acceptable reasons are narrower than most people assume. Appeals must be made within 30 days of the penalty notice. After that, you need HMRC’s permission to appeal out of time, which isn’t guaranteed.
In my experience, the appeals that succeed are always the ones with a specific, documented, external reason for the failure. Serious illness, your own or an immediate family member’s, with medical evidence. A bereavement. A flood or fire destroying records. Reasonable excuses that are generally not accepted include: forgetting the deadline, pressure of work, relying on an agent who failed to file on time, or not knowing you needed to file.
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The “my accountant didn’t file it” excuse Honestly, this one stings to tell clients, but it’s true: relying on your accountant or agent and them failing to file is not accepted by HMRC as a reasonable excuse for late filing. The obligation is yours. You can pursue a complaint against the agent separately if negligence was involved, but HMRC won’t waive the penalty on that basis. Make sure you understand your own filing calendar regardless of who handles the submissions. |
Appealing a penalty-how to do it
Write to HMRC within 30 days of the penalty notice, clearly stating the specific reason for the late filing and including any supporting documentation – medical certificates, death certificates, insurance claim references. You can also appeal online through your HMRC online account. Phone appeals are not accepted. If HMRC rejects your appeal, you can escalate to an independent tax tribunal, but that process takes months and is only worth pursuing for significant penalty amounts.
The honest verdict
There’s a version of this conversation I used to have where I could tell clients that CIS late filing penalties were manageable and that HMRC’s enforcement was soft enough that a late return here and there wasn’t catastrophic. That conversation doesn’t apply anymore.
The April 2026 changes have removed the informal leniency that’s existed since 2015. The nil return requirement is back, the full penalty structure is live, and HMRC has demonstrably more enforcement appetite than it did even eighteen months ago. The anti-fraud measures that came in alongside the penalty changes aren’t just about obvious bad actors – they extend to supply chain accountability for ordinary contractors.
The bottom line
The 19th of every month is a hard deadline. Not a guideline. Not something you can occasionally catch up on without consequences. If you’re not paying subcontractors that month, an inactivity notification takes two minutes and costs nothing. If you are paying subcontractors, your return has to be in by the 19th. Full stop.
The contractors who end up with large penalty bills in 2026 and 2027 aren’t going to be the ones who never knew CIS existed. They’re going to be the ones who knew, got into a sloppy rhythm during the softened enforcement years, and assumed it would continue. It won’t. This is the new baseline, and it’s stricter than anything construction contractors have faced under CIS in recent memory.
If you’re already behind on returns, the right move is to file everything outstanding immediately and get professional advice on your penalty position, not to wait and see. The longer you leave it, the more expensive it gets. At SKZ CIS Accountants, we deal with CIS compliance issues for contractors regularly. Get in touch before the penalties compound further.
Already behind on CIS returns? Talk to SKZ Accountants.
We’re CIS compliance specialists in Ilford, helping UK contractors get up to date, manage outstanding penalties, and set up systems that mean late filing doesn’t happen again. The sooner you act, the less it costs.
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