If you run a construction business and hire subcontractors, filing a CIS return is one of your monthly responsibilities. It’s how you report payments made under the Construction Industry Scheme (CIS), including how much tax you’ve deducted on behalf of HMRC.

Staying on top of your CIS returns is essential for staying compliant and avoiding costly penalties. But if you’re new to the scheme, it can be difficult to know exactly what’s required.

This guide breaks down the essentials. You’ll learn what a CIS return is, who needs to submit one, what information it must include and how to file it correctly each month. We’ll also explain what to do if you make a mistake or miss a deadline and how CIS returns affect your subcontractors.

What is a CIS return?

A CIS return is a monthly report that contractors must send to HMRC as part of the Construction Industry Scheme (CIS). It details all payments made to subcontractors in the previous tax month, along with the tax deductions withheld.

The purpose of the CIS return is to make sure the correct amount of tax is being collected and reported. When you pay a subcontractor, you’re required to deduct tax at the appropriate rate and pass it on to HMRC. The return is your formal record of those transactions.

Submitting accurate CIS returns is a key part of staying compliant with HMRC CIS rules. It ensures that your subcontractors’ tax is correctly recorded and helps prevent issues like penalties, interest or delays in refunds later on.

Who needs to submit a CIS return?

Contractors registered under the Construction Industry Scheme are responsible for submitting CIS returns. If you pay subcontractors for construction work, HMRC likely considers you a contractor, even if construction isn’t your main business. You’re classed as a contractor if:

  • You run a business that pays subcontractors for construction work: You spend more than £3 million on construction in any 12-month period, even if you’re not in the construction industry full-time

Examples include property developers, building firms, or even large businesses managing refurbishment projects. Subcontractors do not file CIS returns themselves, it is entirely the contractor’s responsibility.

If you’re not sure whether you fall under the contractor category, it’s best to check with HMRC or a trusted tax expert.

  • You're a self-employed construction worker: You're a subcontractor and you receive payments under the CIS scheme, you're legally obligated to complete self-assessment tax returns. However, if you don't register for the Construction Industry Scheme, you'll be taxed at the higher 30% rate.

What information goes on a CIS return?

 Each CIS return must include a clear and complete record of the payments you’ve made to subcontractors in the previous tax month and the tax you’ve deducted. Getting the details right matters, as errors can lead to penalties or delays for both you and your subcontractors. Here’s what you’ll need to include:

  • Subcontractor details — Name, Unique Taxpayer Reference (UTR), and National Insurance or company registration number.
  • Payment amounts — Total paid to each subcontractor before deductions.
  • CIS deductions — The tax amount withheld, based on their verification status (20%, 30% or 0% if gross paid).
  • Verification numbers — HMRC issues a unique verification number when a subcontractor is first checked, this must be included if they’re not already registered for gross payment.
  • Nil return status — If you haven’t paid any subcontractors that month, you still need to file a return – this is called a nil return.

Keeping accurate records of these details throughout the month will make filing much easier and help you stay compliant.

How often do you file a CIS return?

CIS returns must be filed every month, covering payments made to subcontractors during the previous tax month. A tax month runs from the 6th of one month to the 5th of the next. For example, payments made between 6th August and 5th September must be reported by 19th September.

Even if you didn’t make any payments in a given tax month, you still need to submit what’s known as a nil return. This tells HMRC that no payments were made, and skipping it can still result in penalties.

Filing on time each month is essential. It keeps your records up to date and ensures subcontractors’ tax deductions are recorded properly.

CIS return deadlines and penalties

The deadline to file your CIS return is the 19th of each month, following the end of the tax month. So if you made payments between 6th August and 5th September, you must submit your return by 19th September. Missing the deadline can lead to automatic penalties from HMRC:

  • £100 if you’re just one day late
  • £200 if it’s over 2 months late
  • £300 or 5% of the CIS deductions if over 6 months late
  • Further £300 or 5% if it’s more than 12 months overdue

In some cases, HMRC may also charge daily penalties or add interest to any late payments. These charges add up quickly, so it’s important to act fast if you’re running behind. Even filing a nil return late can trigger a fine.

HMRC deadlines & penalties

What if I didn’t make any payments this month?

Even if you didn’t pay any subcontractors in a tax month, you’re still required to file a CIS return. In this case, it’s called a nil return.

A nil return simply tells HMRC that no payments were made during the reporting period. It’s a legal requirement, just like a regular CIS return and missing it can result in the same penalties.

This applies whether you’re between projects, haven’t hired subcontractors that month, or paused work for any reason. Filing a nil return ensures your records stay up to date and avoids compliance issues down the line.

Can I amend a CIS return if I make a mistake?

If you realise there’s an error after submitting your CIS return, you can amend it.

Most commercial CIS software allows you to correct and resubmit the return. If you filed through the HMRC CIS online service, you might need to contact HMRC directly to make changes. Either way, it’s important to act quickly to avoid any potential penalties or delays for your subcontractors.

Common mistakes include incorrect payment amounts, wrong deduction rates, or missing subcontractor details. Before submitting each return, double-check the information against your records to make sure everything is accurate.

Keeping good records throughout the month will make it easier to spot and fix any issues before they become a problem.

How do I file a CIS return?

Filing a CIS return doesn’t need to be complicated, but it does require good organisation and accurate records. Here’s a step-by-step guide to help you through the process:

  • Gather your records — Collect all the necessary details for each subcontractor you’ve paid during the tax month, including payment amounts, deductions and HMRC verification numbers.
  • Log in to your CIS filing system — You can file your return using the HMRC CIS online service or through approved commercial software. Make sure you’re registered and have access in advance.
  • Enter the required information — Fill in the details of each subcontractor payment and deduction. If you didn’t pay anyone, you must still submit a nil return.
  • Submit by the 19th — File your return by the 19th of the month following the end of the tax month to avoid penalties.
  • Save confirmation and keep records — Keep a copy of the submission receipt and maintain clear records in case HMRC requests further information later.

CIS return checklist

Before you file your next CIS return, make sure you’ve got everything you need. Use this checklist to stay organised and avoid delays or errors:

Full name and UTR for each subcontractor.
Payment dates and gross amounts.
CIS deductions applied.
HMRC verification numbers.
Nil return status.
Confirmation that all details are accurate and complete.

Staying on top of your records each month makes CIS filing simpler and helps keep things running smoothly with HMRC.

How RIFT can help

Submitting CIS returns is a regular part of running a construction business and getting it right matters. With clear records, a good routine and an eye on your deadlines, it doesn’t have to be a headache.

Filing on time each month keeps you compliant, protects your subcontractors’ tax positions and helps you avoid penalties. Whether you’re new to the scheme or just want peace of mind, the key is knowing what’s required and staying organised.

Expert insights from Helen, Assistant Operations Manager at RIFT

Get organised early: Whether it’s handwritten in a notebook or documented on a fancy spreadsheet, track subcontractor payments and related taxes as they occur. Document names, verification numbers, hours, gross pay, materials costs, deductions - everything in real time. Clean, accurate records make last-minute filing much easier.

Don’t be late: HMRC charges steep fines for missing submission deadlines. Mark the 19th of each month in your calendar with alerts leading up to it. Being organised beats last minute scrambles.

Check your maths: Before hitting submit, double check all the numbers on your return. Make sure subcontractor names, pay info, materials costs and deductions square up. Small mixups can cause audits.

Call in a pro: Tax specialists like RIFT can handle CIS scheme intricacies so you can focus on the job. We aim to make CIS returns easier, seeking to reclaim maximum funds while resolving any issues with HMRC quickly, before they snowball. 

Unlike accountants who charge per hour, our single is for an all-in-one service which includes switching from your previous accountant, avoiding penalties due to late return and yearlong aftercare and advice whenever you need it.

Go digital: Cloud accounting software can automate tedious tasks and streamline messy paperwork. Accounting software can handle estimates, schedules, invoices, payments, deductions, monthly reports, and tax filings all in one place. Less manual work means fewer human errors. Plus, cloud access lets you or your accountant log in from any device or location to stay on top of details. This is great for general contractors managing multiple sites or busy subcontractors that are always on the go.

When you stay diligent, CIS reporting doesn't need to be a headache. Lean on specialist expertise so you never pay more than you owe.

If you are due a CIS tax refund, acting quickly secures your payout faster. Verify your eligibility through RIFT’s user-friendly CIS tax rebate calculator. In a matter of moments you'll see if you have hundreds or thousands coming back. Don’t risk future fines or audits either - getting compliant protects your interests.

CIS tax rebate calculator

For personalised guidance from registration through filing, RIFT specialists make CIS simple. We maximise your deduction accuracy while resolving any issues with HMRC directly on your behalf. Recover every pound possible from self-employment, employment or CIS work while avoiding penalties.

Frequently asked questions

What is the CIS monthly return used for?

To report subcontractor payments and tax deductions to HMRC.

What happens if I don’t file a CIS tax return?

You could face fines, interest charges and compliance issues with HMRC.

Can I skip a CIS return if I didn’t pay anyone?

You must file a nil return even if no payments were made. Meeting CIS return requirements isn’t just box-ticking. It's a crucial part of staying on the right side of the taxman and ensuring smooth financial reporting.

There are real consequences failing to comply with HMRC, and they often come with a hefty price tag. Late or incorrect filings may result in financial penalties, and these can quickly add up. Worse still, non-compliance can open the door to legal issues, which is the last thing anyone in construction needs. Not submitting CIS returns isn’t ‘playing hardball’. It actually puts your business and finances at risk.

Timely submissions mean steering clear of those pesky fines. Keeping your finances in order ensures you're not needlessly parting with your hard-earned cash. By dotting the I's and crossing the T's on your CIS returns, you're also building a solid legal foundation. Legal disputes are a headache no construction worker or contractor wants to deal with, and timely submissions help keep those troubles at bay.

I'm a CIS subcontractor - what expenses can I claim?

You can claim for:

  • Equipment, tools and materials including things like maintenance costs for your gear. If you supply your own specialised or protective clothing, you can claim it as an expense. You might even be able to include laundry costs.
  • Travel and transport. When you're shelling out for travel to temporary workplaces, keep track of your mileage, food and accommodation costs. Hold onto receipts . You'll need them to prove what you've spent.
  • Office costs. This can cover anything from internet bills to stationery. Remember you can only claim for legitimate business expenses, though. If you work from home, you might be able to claim for a proportion of your household bills, too.
  • Administrative costs. If you've got people (even family members) helping you with things like bookkeeping, keep records about what they do. There are strict rules about claiming this kind of thing as an expense, but if you're paying them, it might count.

Find out more about the Construction Industry Scheme (CIS) and how to register if you need to.

Read our guide to CIS and Self-Assessment