Complete your CIS monthly compliance

The CIS monthly cycle at a glance

CIS compliance follows a predictable monthly rhythm. The key is understanding that CIS operates on tax months, not calendar months. Each tax month runs from the 6th of one month to the 5th of the next.

This journey takes 10 minutes. By the end, you will have a clear week-by-week workflow you can follow every month.

Your four-week CIS workflow

Breaking the month into weekly tasks makes CIS manageable. Here is what to do each week:

Week 1: Days 6-12 - Start of tax month

The new tax month begins on the 6th. This is your time to:

• Verify any new subcontractors before you pay them
• Check if anyone needs re-verification (not on returns for 2 tax years)
• Make payments and record deductions for all work this period

Week 2: Days 13-19 - Your busiest CIS week

This is the critical week. Two major deadlines fall on the 19th:

Tip: Submit your return by the 17th to allow for any system issues. Problems on deadline day are not accepted as a reasonable excuse.

Week 3: Days 20-22 - Payment window

After filing your return, you have until the 22nd to pay the deductions to HMRC.

Payment reference: Use your 13-character Accounts Office reference. Only add the 4-digit tax year and month suffix if you are paying for a period other than the current one - adding it to an on-time payment for the current period can delay allocation.

Week 4: Days 23-5 - Review and prepare

Use the final days of the tax month to:

• Check your records - Ensure all payments are properly documented
• Chase missing materials evidence - Follow up with subcontractors who claimed materials but have not provided receipts
• Review any errors - If you spot mistakes, plan corrections for next month's return
• Set reminders for next month - Mark the 17th (prepare), 19th (file), and 22nd (pay)

Months when you pay no subcontractors

You still need to tell HMRC something every month. Either file a nil return showing payments of 0, or make an inactivity request if you have stopped using subcontractors for a while. You can make the request when you file a nil return in the CIS online service. It lasts up to 6 months and you can renew it. When you start paying subcontractors again, file a monthly return with the payments, which ends the inactivity period.

Keep your CIS records

Keep a record of the gross amount of each payment your subcontractors invoice, excluding VAT, and of every deduction you make. Where you made deductions, keep the cost of materials each subcontractor invoiced, excluding VAT. Keep these records for at least 3 years after the end of the tax year they relate to. HMRC can fine you up to £3,000 if you cannot show them when asked.

If you miss a deadline

File a late return as soon as you can: the penalty starts at £100 and grows at 2, 6 and 12 months late. Pay late deductions straight away, as HMRC may charge interest and penalties. If you disagree with a penalty, appeal within 30 days of the date on the penalty notice, online or in writing. You cannot appeal by phone.

Monthly CIS checklist

Bookmark this checklist and review it each month:

Key dates summary

Related guides

For detailed step-by-step instructions on each part of the CIS process: