CIS Tax Rebate Calculator
Use the CIS tax rebate calculator by entering your total income, tax paid, and any expenses you’ve incurred. The calculator will give you an estimation of how much CIS tax back you can claim.
Use the calculator to work out how much tax you can reclaim.
Calculate Your CIS Tax Rebate Easily
The CIS tax rebate calculator takes your total gross self employed income figure and deducts your expenses to create your profit received.
Your tax free personal allowance is then deducted from your profit to produce your total income on which tax is due.
The calculator then works out a CIS tax refund estimation by working out the difference between the amount of CIS tax already deducted by your contractor and the amount of tax that is owed on your total income on which tax is due.
The calculator does not take into consideration any other income, for example from PAYE work or any benefits like JSA.
Please note, our CIS tax rebate calculator only gives you an estimation of what you might be entitled to.
What is a CIS tax rebate?
A CIS tax rebate is money that construction workers can claim back from HMRC when too much tax has been deducted from their pay.
When you work as a subcontractor in construction, your contractor must deduct 20% tax (or 30% if you’re not registered) from your payments before paying you.
This system helps ensure everyone pays the correct tax. You qualify for a rebate when you’ve had more tax taken than you actually owe, which often happens when you have work expenses like tools, travel, or materials that reduce your taxable income.
To get your rebate, you need to be a registered subcontractor in construction-related work and file a Self-Assessment tax return after April 5th each year.
Many subcontractors receive substantial rebates—sometimes thousands of pounds—simply by claiming what they’re entitled to.
For example, if you earned £20,000 on a project with £4,000 deducted for tax, but had £3,450 in legitimate business expenses, you could receive a significant portion of that tax back.
Example CIS tax rebate calculation
A practical example demonstrates how a self-employed cis tax calculator works in real-world scenarios.
Consider Sarah, a registered CIS subcontractor working as an electrician throughout the 2024/25 tax year. Her situation illustrates the potential benefits of proper expense tracking and tax planning.
Sarah’s total gross income from various contractors amounts to £45,000 for the tax year.
As a registered CIS worker, contractors deducted 20% tax from her payments, totalling £9,000 in CIS deductions throughout the year.
Her allowable business expenses significantly reduce her taxable income.
- Tool purchases and equipment totalled £3,200, including a new drill set, testing equipment, and hand tools specifically required for electrical work.
- Vehicle expenses calculated using actual costs method reached £4,800, covering fuel, insurance, repairs, and depreciation for business travel between job sites.
- Professional expenses included £800 for accountancy fees, £600 for public liability insurance, and £400 for electrical certification renewals.
- Additional expenses included £1,200 for work clothing and safety equipment, £800 for training courses to maintain her qualifications, and £600 for home office costs covering the space used exclusively for business administration and client meetings.
Her total allowable expenses sum to £12,400, all supported by proper receipts and documentation.
The tax calculation begins with her gross income of £45,000 minus total allowable expenses of £12,400, resulting in taxable profit of £32,600.
Her tax liability calculation shows income tax of £4,520 (20% on income above the personal allowance of £12,570) plus Class 2 National Insurance contributions of £182 and Class 4 National Insurance of £1,731, totalling £6,433 in tax and National Insurance due.
Comparing her total tax liability of £6,433 against CIS deductions of £9,000 reveals a tax rebate of £2,567.
This substantial rebate results from her diligent expense tracking and the difference between the flat 20% CIS deduction rate and her actual tax liability on reduced taxable income.
What do I need to apply for a CIS tax refund?
To apply for your CIS tax refund you must complete your CIS tax return and you’ll need information on all of your income and outgoings.
CIS tax return necessary records:
- A record of your self-employed income like CIS statements from your contractor.
- PAYE employment information for example a P60 or P45.
- Any jobseekers allowance or ESA if claimed.
- Proof of any expenses incurred like a record of your mileage if you used your own car to travel to temporary sites.
Your records should be kept digitally by using third party accountancy software or in an alternative digital format for a six year period.
Your CIS tax return should only include allowable expenses which can be evidenced if HMRC ask. The office can check your tax return before or after a CIS tax refund has been repaid.
If the tax office review your tax return after your CIS refund has been repaid and find that your return is incorrect a request will be made for you to repay some or all of the tax refund received.
Our free CIS tax refund guide is here to explain more about the construction industry scheme and what it means for you.
Eligible expenses for CIS workers
Understanding your cis eligible expenses is crucial for maximizing your tax rebate potential.
As a construction worker operating under the construction industry scheme, you can claim a wide range of business-related expenses that directly reduce your taxable income.
The key principle is that expenses must be wholly and exclusively for business purposes.
Tools and equipment
Sometimes the most significant expense category for construction workers involves tools and equipment.
This includes everything from basic hand tools like hammers and screwdrivers to specialized power tools such as circular saws, drills, and angle grinders.
You can claim the full purchase price of tools with a useful life of less than two years, while more expensive equipment may need to be claimed through capital allowances over several years.
Essential documentation includes original receipts, proof of purchase, and records showing the tools are specifically required for your construction work.
Travel expenses
Vehicle and travel expenses represent another major area where construction workers can achieve substantial savings.
If you use your personal vehicle for business purposes, you can claim either actual costs (fuel, insurance, repairs, MOT, road tax) or use HMRC’s approved mileage rates.
Currently this stands at 45p per mile for the first 10,000 business miles and 25p per mile thereafter.
Keep detailed mileage logs showing dates, destinations, business purposes, and total miles traveled.
Public transport costs for traveling between job sites are also fully deductible with ticket receipts as proof.
Materials and supplies
Materials and supplies directly related to your construction work qualify as allowable expenses.
This covers building materials you purchase yourself, consumables like screws and nails, safety equipment including hard hats and high-visibility clothing, and specialised supplies for specific trades.
The crucial requirement is that these materials must be used exclusively for business purposes rather than personal projects.
Professional fees
Professional services essential to your construction business are fully deductible. Accountancy fees for preparing your tax returns and managing your finances qualify, as do legal costs related to business matters such as contract disputes or employment issues.
Professional indemnity insurance and public liability insurance premiums are also allowable, along with costs for required industry certifications and health and safety training courses.
Use of home
Home office expenses can be claimed if you regularly use part of your home exclusively for business administration.
This might include a dedicated office space where you handle paperwork, meet clients, or store business records.
You can claim a proportion of household expenses including mortgage interest or rent, council tax, utilities, and home insurance.
The proportion must reflect the business use of your home, typically calculated by the percentage of floor space used exclusively for business purposes.
Marketing and advertising
Marketing and advertising expenses help grow your construction business and are fully deductible.
This includes business cards, website development and maintenance, advertising in trade publications, vehicle signage, and promotional materials.
Even networking events and trade show attendance can qualify if they’re directly related to developing your business.
Training and development
Training and professional development expenses are particularly important in the construction industry where regulations and techniques constantly evolve.
Courses that enhance your skills or are required for your work are allowable, including health and safety certifications, equipment operation training, and industry-specific qualifications.
Keep certificates and course invoices as documentation.
CIS tax returns
A CIS tax return has to be received by HMRC to allow for your CIS refund to be repaid by HMRC.
You will need your ten digit unique taxpayer reference number (UTR) which you would have received when you registered for self assessment.
It is usually best to submit your tax return online although you can download a paper copy and send it to HMRC through the post.
If you are a new CIS sub contractor and have not yet registered with HMRC you can do so online and they will set you up as a construction industry scheme (CIS) sub contractor.
CIS tax return deadlines
The CIS tax return deadlines are strict and follow normal self assessment timescales. You normally must submit your tax return on or before the 31st January after the tax year in question has ended.
The deadline is the 31st October if you decide to submit your tax return on paper through the post.
If you don’t send your tax return to HMRC on time you will receive an immediate late filing penalty which can be appealed if you have a reasonable excuse. Further late filing penalties can be issued after 3 months, six months and twelve months.
In cases where you owe HMRC tax you can incur late payment penalties and interest as well as late filing penalties.
The impact of making tax digital on CIS subcontractors
The transition to Making Tax Digital (MTD) represents a significant shift for CIS subcontractors, fundamentally transforming how they manage their tax obligations.
As of April 2026, some subcontractors must embrace comprehensive digital record-keeping systems, moving away from traditional paper-based methods and spreadsheets toward MTD-compliant software that integrates seamlessly with HMRC systems.
Your digital records will have to be used to submit a summary of your business income and expenses every quarter.
Our guide on making tax digital let’s you know more about what you need to do differently when declaring your CIS income to HMRC.
CIS subcontractors earning above £50,000 need to join MTD by April 2026, followed by those earning £30,000-£50,000 in April 2027, and those earning above £20,000 by April 2028.
MTD promises enhanced accuracy through automated calculations, reduced human error, and improved financial visibility through real-time data access.
For subcontractors dealing with irregular income patterns and complex CIS deductions, this real-time insight could prove invaluable for cash flow management, allowing for more informed financial decision-making and potentially smoother tax periods.
CIS Contractors Tax Rebate FAQs
How much CIS tax can I claim back? The amount varies based on your income, expenses, and tax already paid. Typically, construction workers can claim back anywhere from £1,000 to £3,000 per year depending on their circumstances. Our calculator provides a personalised estimate.
How far back can I claim CIS tax rebates? You can claim CIS tax rebates for up to 4 tax years.
Do I need receipts to claim expenses? While HMRC doesn’t always require receipts for every expense, it’s strongly recommended to keep all receipts for at least 6 years. HMRC can investigate your returns and request evidence of claimed expenses.
When will I receive my CIS tax rebate? If you file your Self Assessment online, rebates are typically processed within 5-6 weeks. Filing earlier in the tax year often results in faster processing times than filing closer to the January deadline.
Can I claim for tools and equipment? Yes, tools and equipment necessary for your construction work are allowable expenses. You can either claim the full cost of items with a useful life of less than 2 years, or use capital allowances for longer-lasting equipment.
What if I work both CIS and PAYE jobs? You’ll need to declare both income sources on your Self Assessment. The calculator can account for both income types to provide an accurate rebate estimate.
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