What is the CIS Tax Rebate Calculator?

If you’re working as a subcontractor in the UK construction industry, there’s a good chance you’ve overpaid tax under the Construction Industry Scheme (CIS). Our free CIS tax rebate calculator helps you estimate how much you may be owed by comparing what you’ve paid in CIS deductions to your actual tax liability.

Under CIS, tax is deducted from your payments before you receive them — but this doesn’t take your expenses or tax-free allowances into account. Many subcontractors are entitled to a rebate at the end of the tax year. This CIS rebate calculator helps you get a clearer picture.

How Does the CIS Tax Rebate Calculator Work?

Simply enter the following details into the calculator:

Your gross earnings – the total amount you have invoiced as a subcontractor, before any CIS tax deductions.

CIS Tax Deducted – the amount already deducted from your payments under CIS.

Business Expenses – any costs you’ve included in your invoices as a subcontractor. This will be things like tools, travel, materials, protective gear, etc.

CIS Registration Status – Confirm whether you’re registered for CIS (this affects deduction rates).

The calculator then works out if you might be due a rebate, and how much, by comparing what you’ve already paid in tax via the Construction Industry Scheme with the estimated tax you owe.

Note: This is an estimate. For a full claim, we recommend speaking with a qualified CIS accountant.

What is the Construction Industry Scheme (CIS)?

The Construction Industry Scheme (CIS) is a scheme set up by HMRC for UK construction workers. If you’re a subcontractor, your contractor will deduct tax at source (20% if you are CIS registered, 30% if you are not registered) from your payments and send it to HMRC. This is meant to cover your tax bill in advance, but often results in overpayment.

Example:
Let’s say you earned £35,000 in the financial year. If you are CIS registered, your contractor will have deducted £7,000 (20%) under CIS and paid this to HMRC on your behalf.

You also spent £5,000 on work-related expenses.

After applying your personal tax allowance and deducting expenses, the actual tax you owe might only be around £4,500. This would mean that you’ve overpaid and could be due a rebate of £2,500.

Benefits of Claiming a CIS Rebate

Get Money Back

Many subcontractors overpay by hundreds or even thousands of pounds through the CIS scheme. You can claim back the money you’re owed in a rebate.

Stay Tax Compliant

Filing for a rebate can be done alongside your annual self-assessment, keeping you in line with HMRC requirements.

Offset Business Costs

Your rebate money can be used to help cover tools, fuel, and other expenses you have as a subcontractor.

Fast and Easy Process

With a CIS accountant, rebates can be processed in as little as 2–4 weeks after the tax year ends.

Frequently Asked Questions About CIS Tax Rebates

Am I definitely due a rebate?

Not always. It depends on how much you’ve paid in CIS deductions versus how much tax you’re actually liable for. However, many subcontractors are due a rebate, especially if they had high expenses in that financial year. Use the CIS rebate calculator to get an estimation of whether you’re due a rebate or not.

When can I claim my CIS rebate?

You can file your tax return and claim your rebate from 6. April, at the end of each tax year.

What expenses can I claim?

Legitimate business expenses can include tools, materials, fuel, uniforms, insurance, and more.

How long does it take to get my rebate?

With a completed tax return, HMRC usually processes rebates within 2–6 weeks. Using an accountant can speed this up.

What if I’m not CIS registered?

You’ll likely have had 30% deducted from your subcontractor pay instead of 20%, which makes it more likely you’re due a CIS rebate. But you’ll still need to file a return to claim it.