CIS return deadline: When and how to file your CIS return

Team Nomi

Jul 04, 2026
6 minutes read

• Share On

If you work in construction as a contractor, it is important to keep up with your CIS return deadline. Missing it can lead to HMRC penalties, even if you have no payments to report. 

The deadline is the 19th of every month following the end of the reporting period, and contractors registered under the Construction Industry Scheme (CIS) must usually submit a return to HMRC each month, even in some months with no subcontractor payments.

This guide explains what is a CIS return, when it is due, and how to file it correctly.

What a CIS return is and who needs to file it

A CIS return is a report contractors submit to HMRC under the Construction Industry Scheme (CIS). It records payments made to subcontractors and confirms whether deductions have been taken from those payments.

If you are a contractor paying subcontractors for construction work, you normally need to file a monthly CIS return. Even if you have no subcontractor payments, you must still submit a nil return unless you have told HMRC your business is temporarily inactive under CIS.

Many new business owners assume CIS only applies to large construction firms, but small businesses and companies can also fall under the scheme. Missing this step could lead to penalties and enquiries with HMRC later.

When is your CIS return due?

Knowing the CIS return deadline is essential to avoid fines.

The monthly return period runs from the 6th day of one month to the 5th day of the next month. You must submit your CIS return by the 19th of every month following the end of the tax period.

For example, if your reporting period runs from 6 April to 5 May, your return must be submitted to HMRC by 19th May.

The CIS filing deadline does not change simply because you forgot or got busy with other business work. HMRC may charge automatic penalties for late submissions. Even a one-day delay can result in a fine.

What information is included in a CIS return?

A CIS return typically includes:

• • Contractor details
    • Your business name and Unique Taxpayer Reference (UTR)
    • Employer reference number (if applicable)
  • Subcontractor details
    • Full name of each subcontractor
    • Unique Taxpayer Reference (UTR)
    • Verification status with HMRC
  • Payment details
    • Total amount paid to each subcontractor during the tax month
    • Date(s) of payment
  • Deduction details
    • Amount of CIS tax deducted from each payment
    • Gross and net payment amounts
  • Employment status confirmation
    • Confirmation that payments were made under CIS (not employment payroll)
  • Nil return declaration (if applicable))
    • Confirmation that no subcontractors were paid during the period (if applicable)

How to file your CIS return with HMRC

Filing before the CIS deadline is usually simple when your records are organised.

To submit your return, you need details of subcontractor payments, deduction amounts, and verification information. 

Most contractors file online using HMRC-approved accounting or payroll software, while some work with accountants or bookkeepers for support.

The process usually includes:

1. Gather payment records

Check all payments made to subcontractors during the month and confirm any CIS deductions.

2. Verify subcontractor details

Make sure subcontractors are properly registered and verified with HMRC.

3. Submit the monthly return

Send the return online before the CIS filing deadline and keep a copy for your records.

4. Correct mistakes quickly

If you notice errors after submission, update HMRC as soon as possible to reduce future problems.

Leaving it until the last day often leads to mistakes. Filing early gives enough time to check figures and avoid stress.

What happens if you miss the CIS deadline?

Missing a CIS return deadline can quickly become costly, especially for small businesses and new company owners managing cash flow. HMRC charges penalties for late submissions, and the longer the delay, the higher the cost. 

Along with the filing deadline, it is also important to remember the payment deadlines for CIS deductions:

• • Due date (electronic payment): 22nd of every month
  • Due date (postal payment): 19th of every month

For the latest and complete information, you can check the official HMRC guidance on penalties for late CIS return filing on the government website. This can help you understand how charges may increase if returns are delayed for longer periods.

Conclusion

Keeping on top of your CIS responsibilities can save your business time, money, and unnecessary stress. Understanding when returns are due and filing them correctly helps you avoid penalties and keeps your records in order with HMRC.

Leaving it until the last minute can lead to missed deadlines, costly fines, and added pressure, especially for small businesses and first-time company directors. Planning and keeping accurate records make the process much easier and give you confidence that everything has been handled correctly.

If you are unsure about filing requirements or need support, speaking with an accountant can help you stay compliant and avoid problems later.

Easy CIS compliance with Nomi Software

Avoid late filings, errors, and manual stress with Nomi CIS software. It helps you calculate deductions, manage subcontractor payments, and submit CIS returns to HMRC quickly and accurately.

Stay compliant and save time every month with a simple, automated CIS process designed for accountants, bookkeepers, and contractors.

Frequently asked questions

1. What happens if you file a CIS late?
Ans. You may get an automatic £100 penalty immediately, with further fines increasing the longer it is delayed.

2. How long does it take for HMRC to process a CIS refund?
Ans. HMRC CIS refunds usually take around 4-6 weeks, depending on your case and whether any checks are required.

3. How do I contact HMRC about CIS tax?
Ans. You can contact HMRC CIS support by calling their CIS helpline or using your HMRC online account for messages and updates.

4. How do I do my CIS tax return?
Ans. You submit your CIS return online using HMRC-approved software or through an accountant, including subcontractor payments and deductions.

5. What time does HMRC CIS open?
Ans. HMRC CIS phone lines are generally open Monday to Friday, 8 am to 6 pm (UK time), excluding public holidays.