Why this rule is catching contractors off guard
Most compliance obligations do not disappear for eleven years and then come back. The CIS nil return obligation did. HMRC removed the requirement to file a CIS300 for months with no subcontractor payments in 2015, and from that point contractors operating in quiet months simply did nothing. That changed on 6 April 2026. The obligation is reinstated, the penalty clock restarts on the 20th of each tax month, and HMRC has not issued prominent warnings to the 1.4 million-plus CIS-registered subcontractors and contractors already in the scheme.
The result is predictable. Contractors who have been registered since before 2015 often have no memory of the old requirement. Those who registered after 2015 never knew it existed. Both groups are now exposed to automatic penalties for filing omissions they did not realise they were making.
This page sets out exactly what the rule requires, how the inactivity notification option works, what the penalty ladder looks like, and how to decide, month by month, which filing you need to make.
The rule in plain terms
A contractor registered under CIS must file a CIS300 monthly return by the 19th of the month following each tax month. Tax months run from the 6th to the 5th: so the month ending 5 May 2026 requires a CIS300 filed by 19 May 2026.
Where you made payments to subcontractors during the month, you file a full CIS300 listing each subcontractor, the gross payment, the labour/materials split, and the deduction made (at 0%, 20% or 30% depending on status). That is the return most contractors are familiar with.
Where you made no payments to subcontractors during the month, from 6 April 2026 you must either:
- file a CIS300 nil return for that month by the 19th of the following tax month, or
- use the inactivity notification option in advance (see below).
There is no third option. Silence is not a filing. HMRC's automated systems will treat a missing return, nil or otherwise, as a late return and issue a penalty.
The inactivity notification: a sensible alternative
If you know in advance that you will not be paying any subcontractors for a sustained period, you do not have to file a nil return every single month. You can pre-notify HMRC of inactivity for a period of up to six months. During that window your monthly CIS300 obligation is suspended entirely.
How it works in practice: contact HMRC (via the CIS helpline or online CIS service) before the 19th of the first month you want to treat as inactive. Tell them the period you expect to have no subcontractor payments. HMRC logs the notification and no returns are required for those months.
Three conditions govern the notification:
- It must be made before the filing deadline for the first inactive month, not retrospectively.
- The maximum period is six months. If inactivity continues beyond that, you renew the notification.
- If you make a subcontractor payment during a notified inactive period, you must file a full CIS300 for that month immediately. The notification does not cover a month in which a payment is actually made.
For contractors with genuinely seasonal workflows, sole traders who take on subcontractor help only for certain project types, or main contractors between large contracts, the inactivity notification is a straightforward way to avoid both unnecessary monthly admin and the risk of a forgotten nil return.
The penalty ladder
Late filing penalties for a CIS300 return, including a nil return, escalate automatically on the following schedule:
| Lateness | Penalty |
|---|---|
| 1 day late | £100 |
| 2 months late | £200 |
| 6 months late | £300 or 5% of the CIS liability (whichever is higher) |
| 12 months late | £300 or 5% of the CIS liability (whichever is higher); up to £3,000 or 100% where information is withheld deliberately |
Because a nil return carries a zero CIS liability, the percentage-based stages at six and twelve months will always settle at the £300 floor. The maximum exposure for a single missed nil return is therefore £300 rather than the open-ended sums that can arise on returns with large liabilities. But penalties stack across months. Miss six nil returns in a row and you are looking at penalties of up to £100 per return before the two-month escalation, accumulating while HMRC's systems quietly log each overdue period.
A word on appeals. HMRC can reduce or cancel penalties where there is a reasonable excuse and you file promptly once you become aware. For the first months of the reinstated rule, the fact that the obligation was absent for eleven years is context worth raising in any appeal. It is not a guaranteed outcome, but HMRC has discretion and a persuasive letter filed quickly after a missed return is always better than ignoring the penalty notice.
A simple decision flow for each tax month
At the end of each tax month, work through this in sequence:
Step 1: Did you make any payments to CIS subcontractors during this tax month?
- Yes: file a full CIS300 by the 19th of the following month. Include every subcontractor paid, the gross amount, the labour element (CIS deductions apply to labour only, not materials), the applicable rate (0% for GPS holders, 20% for registered, 30% for unregistered), and the deduction withheld.
- No: proceed to Step 2.
Step 2: Did you pre-notify HMRC of inactivity covering this month?
- Yes: no return needed for this month. But check that the notified period has not expired, and that you made no payments (which would cancel the notification for this month).
- No: file a CIS300 nil return by the 19th of the following month.
That is the full decision. If you are uncertain whether a particular payment counts as a CIS payment for this purpose, file the full return rather than the nil. An unnecessary full return with a legitimate nil result causes no problems. An omitted return triggers penalties automatically.
How this fits into your monthly CIS routine
The nil return obligation sits alongside the other contractor filing duties covered in the CIS monthly returns guide, which covers the full CIS300 submission process, payment deadlines, and how to correct errors on earlier returns. The nil return does not change those obligations; it adds one. Contractors who already file on time each month simply need to add a check: if no payments were made, file nil (or confirm the inactivity notification is in place).
There is also a connection to how CIS works overall. The monthly return is one of the core contractor obligations under the scheme, sitting alongside subcontractor verification and deduction payments to HMRC. If you are new to CIS as a contractor, that overview is the right starting point before drilling into nil return mechanics.
What this means for Gross Payment Status
If you hold Gross Payment Status, or are working towards it, the nil return obligation has a direct bearing on your compliance test. GPS requires all tax obligations to have been met on time for the past twelve months. A pattern of late CIS300 filings, including late nil returns, could put your GPS position at risk when HMRC next reviews it.
From 6 April 2026 the GPS compliance bar is also higher in other respects. Under Finance Act 2026, HMRC can revoke GPS immediately and without notice where a contractor "knew or should have known" about fraudulent supply chain connections, and a five-year reapplication ban applies where GPS is removed on fraud grounds. Keeping your monthly return obligations clean, nil or otherwise, is one part of staying on the right side of the compliance test that underpins GPS.
For a more detailed look at GPS qualification, the April 2026 anti-fraud changes, and how to protect your position, see our CIS gross payment status guide.
Getting returns off your plate
For contractors managing their own CIS300 filings, the nil return adds a low-effort but easy-to-forget obligation. A monthly calendar reminder set to the 15th of each month (giving four days before the 19th deadline) is the simplest way to stay on top of it. Check whether any subcontractor payments went out that month, then file accordingly.
For contractors who would prefer to hand the whole CIS return process to a specialist, including nil months, inactivity notifications, and the full CIS300 filing cycle, our CIS accounting services cover exactly that. The cost of a missed nil return, in penalties and GPS risk, typically exceeds the cost of having it handled for you.