Every CIS monthly return must reach HMRC by the 19th of the month, and a return that is even one day late attracts an automatic £100 penalty [1]. Miss the deadline for two months and the penalty rises to £200, before tax-geared charges begin to stack on top [2]. For a contractor running several jobs at once, the return is the most unforgiving deadline in the Construction Industry Scheme.
A CIS return is the monthly declaration a contractor makes to HMRC listing every subcontractor paid, the amounts, and the tax deducted from each [5]. It is separate from paying the deductions over, and both have their own deadlines. Getting either wrong exposes the contractor to fixed penalties, interest, and in the worst cases a charge of up to £3,000.
This article explains what a CIS return contains, how and when to file it, the nil-return rules, the full penalty ladder for late filing, the deadlines for paying deductions to HMRC, and how limited company subcontractors reclaim the deductions taken from their own income.
Key takeaways
- CIS monthly returns must reach HMRC by the 19th of every month following the tax month.
- A late return triggers an automatic £100 penalty, rising to £200 after two months, then tax-geared charges after six and twelve months.
- A contractor who paid no subcontractors in a month must still file a nil return or notify HMRC of a period of inactivity.
- Deductions are paid separately, by the 22nd if paid electronically or the 19th if paid by post.
- Limited company subcontractors reclaim CIS deductions through the payroll scheme on an Employer Payment Summary, not through the Corporation Tax return.
What a CIS monthly return is
A CIS return, filed on the CIS300 form through HMRC's online service, is a contractor's monthly account of its dealings with subcontractors [1]. Each return covers a tax month running from the 6th of one month to the 5th of the next, and reports the payments made and the deductions taken during that period [5]. The return is the mechanism through which HMRC reconciles what a contractor has withheld against what its subcontractors ultimately owe.
The obligation sits with the contractor, not the subcontractor. Any business that pays for construction work in the course of a construction business, and any deemed contractor whose construction spending crosses the threshold, must file [5]. A contractor that has registered a CIS scheme is expected to file every month, whether or not any payments were made [1].
Who must file and by when
The filing deadline is fixed. A monthly return must reach HMRC by the 19th of the month following the end of the tax month it covers [1]. A return for the tax month running 6 May to 5 June, for example, must arrive by 19 June [1]. There is no monthly variation and no weekend extension built into the rule, so contractors treat the 19th as a hard stop [2].
Every contractor with an active CIS scheme is expected on the system each month. A contractor that files late repeatedly builds a compliance record that can later cost it, or its subcontractor clients, gross payment status under the wider scheme [5]. Accountants running CIS for several clients often centralise the filing calendar so no scheme slips, a discipline that a payroll bureau platform supports by tracking each client's deadline separately.
The information a return contains
Each return lists, for every subcontractor paid, the gross amount excluding VAT, the cost of any materials excluding VAT, and the deduction taken [8]. The contractor also makes two declarations on the return: that the employment status of each subcontractor has been considered, and that every subcontractor listed has been verified where verification was required [5].
The employment status declaration carries teeth. A contractor that gives the wrong employment status for a subcontractor on the return can face a penalty of up to £3,000 [1]. Because CIS applies only to genuinely self-employed subcontractors, a worker who is really an employee belongs on the payroll under Real Time Information, not on a CIS return [8]. HMRC-recognised SME payroll software keeps that boundary clean by handling employees through PAYE while CIS deals only with subcontract payments.
How to file a CIS monthly return
Filing is done electronically through HMRC's CIS online service or through commercial software that submits directly to HMRC [1]. Paper returns were withdrawn for most contractors from 30 April 2016, with a narrow exception for those filing in Welsh [1]. The vast majority of contractors therefore file online or through a payroll product that carries the submission for them.
Filing online or through software
The HMRC CIS online service lets a contractor enter each subcontractor and amount by hand, then submit the return and, if needed, amend it later by selecting "Amend return" from the returns menu [1]. For contractors with more than a handful of subcontractors, commercial software removes the manual entry and reduces the risk of a keying error that would trigger an amendment [1].
Commercial CIS software also enforces one of HMRC's formatting rules automatically: a return must not contain negative values, and any figure that would come to less than zero must be entered as zero instead [1]. Software platforms building construction or field-service tools can go further and embed CIS return logic directly through an HMRC-recognised payroll API, so their users file without leaving the product [5].
Nil returns and inactivity requests
A month with no subcontractor payments is not a month off. A contractor that has paid no subcontractors must either file a nil return showing zero payments, or tell HMRC it has temporarily stopped using subcontractors by making an inactivity request [1]. An inactivity request pauses the monthly filing obligation for up to six months, after which the contractor must file again or renew the request [5].
Skipping a return because no payments were made is a common and costly mistake, because HMRC still issues the automatic penalty for a missing return [2]. HMRC has confirmed that from April 2026 contractors will be required to file a nil return or notify inactivity when they do not pay subcontractors, formalising the position in the scheme's simplification measures [11].
Deadlines and penalties for late CIS returns
The late-filing penalty regime is automatic and escalates on a fixed timetable [3]. It does not wait for HMRC to notice: the charge is triggered by the calendar, and a return filed after the 19th is late by definition [2]. The ladder runs as follows.
| Time after filing deadline | Penalty |
|---|---|
| Return filed late (from the day after the 19th) | £100 fixed |
| 2 months late | £200 fixed |
| 6 months late | greater of £300 or 5% of the CIS deductions on the return |
| 12 months late | a further greater of £300 or 5% of the CIS deductions on the return |
Sources: penalty amounts from HMRC's compliance-checks factsheet [3] and the CIS reform manual [2].
Fixed and tax-geared penalties
The first two penalties are fixed at £100 and £200 and apply regardless of the size of the return [2]. Once a return is six months late, the penalty becomes tax-geared, calculated as the greater of £300 or 5% of the CIS deductions on that return, and the same tax-geared charge repeats at twelve months [3]. In the most serious cases, where HMRC concludes information has been deliberately withheld, the twelve-month penalty can reach the higher of £3,000 or 100% of the deductions on the return [3].
Because the penalties accumulate per return, a contractor who has fallen months behind on several returns can face a bill that dwarfs the tax at stake [4]. This is the practical case for automated filing: the deadline never moves, and software that submits on time removes the single most common cause of the penalty [1].
Capping, appeals and paying a penalty
HMRC applies a cap in one specific situation. When a contractor files a first CIS return and earlier returns are also outstanding, the total of the £100 and £200 fixed penalties for certain of those returns can be capped at £3,000 [2]. The cap is a relief for new contractors caught up in a backlog, not a general ceiling on penalties [2].
A contractor that believes a penalty is wrong, for instance because a return was filed on time but not recorded, can appeal [3]. Where a penalty stands and must be paid, HMRC provides a dedicated route to settle it using the payment reference on the penalty notice [4]. Keeping the filing receipt from each submission is the simplest way to defend an appeal if HMRC's record disagrees with the contractor's [7].
Paying CIS deductions to HMRC
Filing the return and paying the money are two separate obligations with two separate deadlines. The deductions a contractor withholds from subcontractors must be paid over to HMRC alongside its PAYE and National Insurance in a single monthly payment [6]. The payment deadline is later in the month than the filing deadline, which catches out contractors who assume the two align.
| Payment method | Monthly deadline | Quarterly deadline (if eligible) |
|---|---|---|
| Electronic payment | 22nd of the following month | 22nd of the month the quarter ends |
| Payment by post | 19th of the following month | 19th of the month the quarter ends |
Sources: payment deadlines from HMRC guidance on paying deductions [6].
Smaller contractors may be eligible to pay quarterly rather than monthly, with tax quarters ending on 5 July, 5 October, 5 January and 5 April [6]. Whatever the frequency, a single payment covers PAYE tax, National Insurance and CIS deductions together, and late payment attracts interest and possible penalties [6]. Because the payment and the return share the same underlying figures, a contractor that files accurately has already done the arithmetic the payment requires [8].
Payment and deduction statements and record keeping
A contractor that makes a deduction must give the subcontractor a payment and deduction statement within 14 days of the end of the tax month [7]. This statement is the CIS equivalent of a payslip and is the subcontractor's evidence of tax already paid, so it must show the gross amount, the materials excluded, and the deduction taken [8]. A subcontractor cannot reclaim a deduction it cannot evidence, which makes the statement as important to the payee as the return is to HMRC [9].
Record keeping is a legal obligation in its own right. A contractor must keep its CIS records, including the gross amount of each payment, the deduction made and any materials cost, for at least three years after the end of the tax year they relate to [7]. HMRC can ask to see those records at any time, and a contractor that cannot produce them can be fined up to £3,000 [7]. A business issuing one-off statements can produce compliant documents through an instant payslip generator where a full payroll product is not warranted.
How limited company subcontractors reclaim deductions
A limited company that is paid under deduction as a subcontractor does not wait until the year end to recover the tax withheld. It sets the CIS deductions suffered against the PAYE, National Insurance, student loan and CIS liabilities it owes as an employer, reporting the running total on its monthly or quarterly Employer Payment Summary [9]. HMRC then reduces the company's PAYE bill by the deductions claimed, and the company pays only the balance [10].
The route matters. A company must reclaim CIS through its payroll scheme on the EPS, and must not attempt to recover it through the Corporation Tax return, which can trigger a penalty [9]. Where a company's PAYE bill for the period falls to zero and deductions remain, the excess carries forward to the next month or quarter within the same tax year [10]. Any surplus still unused at the year end can be refunded or set against Corporation Tax once the final PAYE and CIS submissions are in [10]. Contractors new to the mechanics can read the Moonworkers guide to payroll for construction and CIS for the wider picture.
Conclusion
The CIS return is a fixed monthly rhythm rather than an occasional task, and the businesses that stay clear of penalties are those that treat the 19th as immovable and file every month without exception, nil returns included. The penalty ladder is unforgiving precisely because it is automatic, and the cheapest way to avoid it is to never miss the date.
As HMRC formalises the nil-return obligation from April 2026 and continues to tighten the scheme against supply-chain fraud, the administrative bar only rises. Contractors and the accountants who serve them are moving towards systems that file on time by default and reconcile the return against the payment automatically, so compliance becomes a property of the software rather than a monthly scramble.
Frequently asked questions
When is the CIS return deadline each month?
A CIS monthly return must reach HMRC by the 19th of the month following the tax month it covers, and a tax month runs from the 6th to the 5th [1]. A return covering 6 April to 5 May, for instance, is due by 19 May. The deadline does not shift for weekends, so contractors treat it as a hard cut-off to avoid the automatic penalty [2].
Do contractors have to file a CIS return if they paid no subcontractors?
Yes. A contractor with an active CIS scheme that paid no subcontractors in a month must file a nil return or notify HMRC of a period of inactivity, which pauses filing for up to six months [1]. Simply skipping the return still triggers the automatic £100 penalty. From April 2026 the requirement to file a nil return or report inactivity is being formalised in the scheme's rules [11].
What is the penalty for filing a CIS return late?
A late return attracts an automatic £100 penalty, rising to £200 once it is two months late [2]. At six months and again at twelve months, the penalty becomes tax-geared, set at the greater of £300 or 5% of the CIS deductions on the return [3]. In serious cases the twelve-month penalty can reach the higher of £3,000 or 100% of the deductions.
How does a limited company claim back CIS deductions?
A limited company subcontractor reclaims CIS deductions through its payroll scheme, entering the year-to-date total on its Employer Payment Summary so HMRC offsets it against the PAYE and National Insurance the company owes [9]. It must not reclaim through the Corporation Tax return, which can lead to a penalty [10]. Any deductions that cannot be offset within the tax year can be refunded or set against Corporation Tax at the year end.
Image prompt: A wide realistic landscape photograph of a UK construction contractor's site office at dusk, a person at a laptop reviewing a payment schedule with a hard hat resting on the desk and a building site visible through the window, warm interior light, muted natural tones, documentary style, shallow depth of field, no text, no logos, shot on a 35mm lens.
