For a busy construction business, the question “when are CIS returns due?” usually appears when the 19th is getting close and there are still invoices, timesheets and subcontractor details to sort out. The good news is that the rule is straightforward once you know how the CIS tax month works. The key is to keep records up to date, rather than trying to rebuild them at the last minute.
When are CIS returns due?
A CIS monthly return must reach HMRC by the 19th of the month after the tax month ends.
The CIS tax month runs from the 6th of one month to the 5th of the next. For example, payments you make to subcontractors between 6 April and 5 May must be included on a CIS return submitted by 19 May.
This is a monthly obligation for contractors registered for the Construction Industry Scheme, even where the deadline falls at an inconvenient time. It helps to think of the 5th as your monthly cut-off point, then allow enough time to check the figures and submit the return before the 19th.
The return covers payments made to subcontractors, not simply invoices received. If a subcontractor sends an invoice on 4 May but you pay it on 7 May, that payment normally belongs in the following CIS tax month.
A simple CIS return deadline example
Here is how the dates work in practice. If you pay a subcontractor at any point from 6 June to 5 July, those payments fall into the July CIS tax month. Your return is then due by 19 July.
This can catch out businesses that pay subcontractors weekly, fortnightly or on different dates each month. A well-organised payment record is far more useful than a pile of invoices when it is time to prepare the return. You need to be able to see the date paid, the labour amount, any materials amount and the tax deduction made.
If you also run payroll, it is worth keeping CIS records clearly separate from employee wages. CIS is not a substitute for PAYE, and deciding whether someone is genuinely self-employed for tax purposes should never be based on what is easiest administratively.
What needs to go on a CIS monthly return?
Each monthly return tells HMRC about payments made to subcontractors under CIS. Before paying a new subcontractor, you should verify them with HMRC. The verification result confirms whether they should be paid gross, or whether you need to deduct tax at the standard or higher rate.
For each relevant payment, your records should show the subcontractor’s details, the gross amount of labour, the cost of materials where applicable, and the CIS deduction. Materials are not normally subject to CIS deductions, but they must be genuine materials costs and properly evidenced.
You also make declarations on the return, including that the subcontractors shown are not employees. This is why getting worker status right matters. Calling somebody a subcontractor does not automatically make them self-employed. Their working arrangement, level of control, financial risk and other practical factors all need consideration.
After making deductions, contractors should provide subcontractors with a deduction statement. This helps them claim credit for tax already deducted when they complete their own tax return or deal with their accountant.
Do you need to submit a return if you have paid nobody?
Usually, yes. If you are registered as a CIS contractor but have not paid any subcontractors during the tax month, you should submit a nil return by the same deadline. A nil return confirms to HMRC that there is nothing to report, rather than leaving them to assume the return has been missed.
There is an alternative if you know you will not be paying subcontractors for a period. You may be able to tell HMRC that your scheme is inactive for a set time. This can reduce unnecessary monthly filing, but it is only suitable where there really will be no subcontractor payments. If plans change and you pay someone, you will need to reactivate your CIS reporting promptly.
For a small builder, property developer or trades business, this is one of those jobs that is easy to overlook during a quiet patch. A quick review after the 5th of each month can prevent an avoidable late-filing problem.
What happens if your CIS return is late?
HMRC can charge penalties for late CIS returns. The first penalty can arise as soon as the return is one day late, so waiting until the end of the month is not a safe option. Further penalties may increase the longer the return remains outstanding.
A late return can also create unnecessary stress if you need to correct payroll records, explain deductions to subcontractors or reconcile what you owe HMRC. If tax deductions have been made, those amounts need to be paid to HMRC too. The payment deadline is normally the 22nd of the following month when paying electronically, although the deadline may be earlier for non-electronic payments.
Submitting the return and paying the deductions are related but separate responsibilities. Filing the return on time does not remove the need to pay what is due, and making a payment does not replace the return.
If you have missed a deadline, do not ignore it. Submit the outstanding return as soon as possible, check whether the figures are accurate and deal with any payment due. Where there is a reasonable explanation, it may be worth seeking advice on your position, but it is always better to act quickly.
How to make monthly CIS returns less stressful
The most reliable approach is a simple monthly routine. Once the tax month closes on the 5th, gather the payment information for every subcontractor paid during that period. Check that each person was verified before payment, that the correct deduction rate was used and that any materials costs have been recorded separately.
Then reconcile the deductions to your bookkeeping records before submitting the return. This is particularly helpful if you use cloud accounting software, as payments may have been made by bank transfer, card or cash and can otherwise be missed or duplicated.
Leave a few days before the 19th for queries. A subcontractor may send a corrected invoice, a materials figure may need clarification, or you may find that a payment was allocated to the wrong person. Filing on the 18th every month leaves little room for those ordinary admin issues.
Many small firms find it useful to set two recurring reminders: one shortly after the 5th to prepare the records, and one several days before the 19th to submit and check payment arrangements. If you work with a bookkeeper or payroll provider, agree who supplies the information, who reviews it and who presses submit. Clear responsibility avoids assumptions.
Common CIS mistakes to watch for
The deadline itself is only one part of staying compliant. Common problems include deducting CIS from the full invoice including materials, paying a subcontractor before verifying them, or including an invoice in the wrong month because the payment date was not checked.
Another frequent issue is mixing CIS records with general business expenses. A payment to a supplier is not automatically a CIS payment, and a subcontractor may supply both labour and materials. Clear descriptions and properly retained invoices make the distinction much easier to support.
Accuracy matters more than speed, but neither should mean working late on the 18th every month. Good bookkeeping gives you a clear view of what has been paid and what tax has been withheld, so your CIS return becomes a routine part of running the business rather than a monthly worry.
If the dates, deductions or worker-status questions are taking time away from your projects, friendly hands-on support can make a real difference. A calm monthly process gives you space to focus on the work your customers are paying you to do.