CIS Tax Return 2025–2026: Leader Accountancy Milton Keynes
If you are a CIS subcontractor or contractor in the UK, the 2025–2026 financial year is critical. With increased HMRC compliance checks and a strict Self Assessment deadline of 31 January 2027, filing your CIS Tax Return correctly has never been more important.
This in-depth guide explains everything you need to know about CIS tax for the 2025–2026 tax year, including deadlines, refunds, expenses, common mistakes and why working with a trusted CIS accountant in Milton Keynes can protect your income and maximise your tax refund.
What Is CIS and How Does It Work?
The Construction Industry Scheme, commonly known as CIS, is a UK tax system that applies to contractors and subcontractors working in the construction industry.
Under CIS, contractors deduct tax from subcontractors’ payments and send it directly to HMRC. These deductions act as advance payments towards the subcontractor’s annual tax bill.
However, CIS deductions do not replace your tax return. You must still file a Self Assessment Tax Return every year to declare:
- Total CIS income
- Tax already deducted by contractors
- Allowable business expenses
Failing to submit a correct CIS Tax Return can result in penalties, delayed refunds or HMRC investigations.
Who Needs to File a CIS Tax Return for 2025–2026?
You are required to file a CIS Tax Return if any of the following apply during the 2025–2026 tax year:
- You worked as a CIS subcontractor
- You had CIS tax deducted from your payments
- You are registered for Self Assessment
- You received additional income alongside CIS work
This applies whether you are self-employed, a sole trader or operating through certain limited company arrangements.
CIS Tax Return Deadlines for the 2025–2026 Financial Year
Understanding deadlines is essential to avoid penalties.
- Tax year covered: 6 April 2025 to 5 April 2026
- Self Assessment filing deadline: 31 January 2027
- Tax payment deadline: 31 January 2027
HMRC applies automatic late filing penalties starting at £100, even if you do not owe any tax or are due a refund.
Monthly CIS Obligations for Contractors
If you are a contractor, you also have monthly CIS responsibilities.
- Monthly CIS returns must be submitted by the 19th of each month
- Returns cover payments made between the 6th and 5th
- Late submissions result in automatic penalties
How to File Your CIS Tax Return Correctly
Filing a CIS Tax Return requires accuracy and good record keeping.
- Register for Self Assessment with HMRC
- Collect CIS deduction statements from all contractors
- Calculate total CIS income for the year
- Include all tax already deducted
- Claim allowable business expenses
- Review figures carefully
- Submit your return online before 31 January 2027
Allowable Expenses for CIS Subcontractors
Claiming expenses correctly is one of the most effective ways to reduce your tax bill and increase your CIS refund.
- Tools and equipment
- Protective clothing and safety gear
- Work-related travel and mileage
- Vehicle costs used for business
- Mobile phone and internet
- Accountancy and bookkeeping fees
All expenses must be wholly and exclusively for business purposes and supported by records.
CIS Tax Refund Explained
Many CIS subcontractors overpay tax during the year because deductions are taken at a flat rate.
Example: If £8,000 was deducted from your CIS income but your final tax liability is £5,500 after expenses, HMRC may refund £2,500.
This refund is only issued if your CIS Tax Return is filed accurately and on time.
Common CIS Tax Return Mistakes
- Missing CIS deduction statements
- Incorrect income figures
- Not claiming all allowable expenses
- Late filing
- DIY submissions with errors
These mistakes often result in lost refunds or HMRC penalties.
Why CIS Compliance Is More Important Than Ever
HMRC continues to increase digital compliance checks and cross-references CIS data with Self Assessment submissions.
Errors are now identified faster, and penalties are issued automatically. Professional support reduces risk and ensures accuracy.
CIS Accountant in Milton Keynes
Leader Accountancy is a trusted accounting firm supporting CIS subcontractors and contractors in Milton Keynes and across the UK.
- CIS Tax Return preparation
- Maximising CIS refunds
- Self Assessment filing
- Monthly CIS compliance
- Clear communication and expert advice
Need Help With Your CIS Tax Return 2025–2026?
Speak to a trusted CIS accountant in Milton Keynes and file with confidence. Book Your CIS Consultation
Frequently Asked Questions – CIS Tax Return 2025–2026
Do I need to file a CIS Tax Return if tax was already deducted?
Yes. CIS deductions are advance payments. You must still submit a Self Assessment Tax Return.
What is the CIS Tax Return deadline?
The deadline for the 2025–2026 tax year is 31 January 2027.
Can I get a CIS tax refund?
Yes. If you overpaid tax under CIS, HMRC may issue a refund after processing your return.
Should I use an accountant for CIS?
An accountant helps maximise refunds, reduce errors and avoid penalties.