CIS Monthly Return: How to File with HMRC and Key Deadlines Explained

 

 

 

 

 

 

Filing your CIS monthly return

Step 1

Register for a CIS account with HMRC.

Step 2

Collect all relevant payment details and deductions.

Step 3

Complete the return using HMRC online services.

Step 4

Submit your return by the deadline.

What Is a CIS Monthly Return?

Under the Construction Industry Scheme (CIS), contractors in the UK must report payments made to subcontractors and the tax deducted from those payments to HM Revenue & Customs (HMRC) every month. This monthly report is known as a CIS monthly return (form CIS300). Its purpose is to help HMRC ensure correct tax deductions and compliance in the construction sector.

Key Elements Reported in a CIS Return

  • Name of each subcontractor paid
  • Unique Taxpayer Reference (UTR) and verification number
  • Gross amount paid (before tax)
  • Amounts deducted under CIS
  • Confirmation that subcontractors are not employees (classification)

Who Needs to File a CIS Return?

Contractors

You must file a CIS monthly return if you are:

  • Registered as a CIS contractor with HMRC
  • Paying subcontractors for construction work in the UK

Contractors include companies, partnerships, and sole traders that make construction payments to subcontractors that require CIS deductions. Subcontractors do not file the CIS monthly return; instead, they receive payment and deduction statements and include these in their own annual returns if necessary.

When Is the Monthly CIS Return Deadline?

Filing Deadline

  • By the 19th of the month following the end of the CIS tax month. 

Tax Month Definition

  • CIS tax months run from 6th of one month to 5th of the next.
    Example: Payments from 6 May – 5 June must be reported by 19 June.

If No Payments Were Made

Even if you made no payments to subcontractors, you must either:

  • Submit a nil return reporting zero payments, or
  • Notify HMRC that no return is due for that period

Failing to do so may lead HMRC to treat your return as late.

How to File the CIS Monthly Return with HMRC

You can file your CIS monthly return in any of the following ways:

  1. HMRC Online Services
    Log in to your Government Gateway account and use HMRC’s CIS online service to submit the CIS300 return.
  2. Commercial CIS/Accounting Software
    Approved software (e.g., Xero, QuickBooks, Sage) can generate and submit the return directly to HMRC.
  3. Through an Accountant/Tax Agent
    A qualified accountant or agent can prepare and send the return on your behalf

Information Required on the Return

  • Contractor name and details
  • Subcontractor details (name, UTR, verification status)
  • Payment amounts and CIS deductions
  • Confirmation of subcontractor classification

Payment of CIS Deductions and Additional Deadlines

In addition to filing the return, you must pay the tax deducted to HMRC:

Payment deadlines for CIS deductions:

  • By the 22nd of the month if paying electronically
  • By the 19th if paying by cheque or post
  1. Penalties for Late or Missing CIS Returns

If you miss the reporting deadline, HMRC can impose automatic penalties:

  • 1 day late: £100
  • 2 months late: £200
  • 6 months late: £300 or 5% of CIS deductions (whichever is higher)
  • 12 months late: £300 or 5% of CIS deductions (whichever is higher)
  • Over 12 months late: up to £3,000 or 100% of the deductions (whichever is higher) 

Penalties can be canceled if you inform HMRC that no payments were made in that period.

Record-Keeping Requirements

HMRC requires that you keep records of subcontractor payments and deductions for at least three years after the end of the relevant tax year in case they request to see them.