CIS deductions are not a final tax. They are an advance payment - HMRC collecting estimated tax at source before the year is settled. If your actual UK tax liability is lower than the amount deducted under CIS, HMRC owes you the difference. For many Irish tradespeople who work in the UK for part of the year, this difference is significant.
The refund does not come automatically. You have to claim it, through a UK self-assessment tax return. HMRC will not contact you to advise that you are owed money.
This article covers the reclaim process in full.
Why Most Irish Tradespeople Are Owed a Refund
CIS deductions are calculated on gross labour payments at 20% or 30%, without any allowance for the expenses of the work - travel, tools, accommodation, materials. The actual UK tax due on your UK earnings, after allowable expense deductions, is almost always lower than the CIS deductions made.
Consider a practical example. An Irish electrician works in London for four months and receives gross labour payments of 20,000 pounds, with CIS deducted at 20% - 4,000 pounds to HMRC. His allowable expenses for those four months are:
Travel (flights or ferry from Ireland): 1,200 pounds. Accommodation in London: 4,800 pounds. Tools and equipment used on the work: 600 pounds. Other work-related costs: 400 pounds.
Total expenses: 7,000 pounds. Net UK taxable income: 13,000 pounds.
UK income tax on 13,000 pounds, after the UK personal allowance of 12,570 pounds, is approximately 86 pounds (20% on the 430 pounds above the personal allowance).
CIS deducted was 4,000 pounds. UK tax due is approximately 86 pounds. Refund owed: approximately 3,914 pounds.
This is not unusual. Irish tradespeople who work in the UK for part of the year and have significant travel and accommodation costs regularly have nearly all of their CIS deductions refunded.
Step 1: Register for UK Self-Assessment
To file a UK tax return and claim the CIS refund, you must be registered for UK self-assessment with HMRC.
If you have a UK National Insurance number (most Irish nationals who have worked in the UK do), you register online at gov.uk. The registration creates your Unique Taxpayer Reference (UTR) number, which you need to file the return.
If you do not have a UK National Insurance number, you can apply for one through the UK Department for Work and Pensions (DWP). This can be done from Ireland but takes several weeks. Start this process early.
Step 2: Collect Your CIS Deduction Statements
Every contractor who made CIS deductions from your payments must give you a CIS deduction statement for each tax year. This statement shows your gross payment and the amount deducted. You need these statements to complete the UK tax return - they provide the official record of what was deducted on your behalf.
If you did not receive CIS statements from contractors, ask for them. You are legally entitled to them. In practice, many Irish tradespeople leave the UK without collecting these - chasing them from abroad is more difficult but not impossible.
Step 3: Gather Your UK Work Expense Records
For every expense you intend to claim against your UK earnings, you need supporting evidence - receipts, bank statements, booking confirmations. The categories of allowable UK construction expenses mirror the Irish position broadly:
Travel between Ireland and the UK for work. Accommodation costs while working away from your Irish base. Meals while working away (at standard HMRC approved rates or with receipts). Tools, safety equipment, workwear. Any other costs wholly and exclusively incurred for the UK work.
The dual Irish/UK nature of your situation is relevant here. Travel from Ireland to the UK is a legitimate expense of the UK work. HMRC accepts this.
Step 4: File the UK Self-Assessment Return
The UK tax return covering construction income and CIS deductions is the SA100 (main return) plus SA103 (self-employment supplement). The return covers the UK tax year, which runs 6 April to 5 April - different from the Irish January to December tax year.
On the return you declare:
Your gross UK construction income. Your allowable UK work expenses. The CIS deductions made from your payments.
HMRC calculates your tax due and compares it to the CIS deductions. The difference - typically a refund - is paid directly to your UK bank account, or to an Irish bank account if you provide those details.
Step 5: Declare the UK Income on Your Irish Return
This is the step that many Irish tradespeople who do manage to reclaim their CIS miss entirely. Ireland taxes its residents on worldwide income. Your UK construction earnings must appear on your Irish Form 11 income tax return.
The UK income is declared under Case III (foreign income). The UK income tax paid is credited against your Irish tax liability on that income under the Ireland-UK double taxation agreement - in most cases, because the UK tax after the personal allowance is very small, the Irish tax will also be minimal or nil, but the income must be declared.
Failing to declare UK income on the Irish return creates a separate Irish compliance exposure, regardless of whether the UK side has been correctly handled.
How Far Back Can You Claim?
UK self-assessment returns can be filed up to four years after the end of the relevant UK tax year. The UK tax year ends 5 April, so you can currently file returns back to the 2021-2022 tax year (ended 5 April 2022) in addition to more recent years.
If you worked in the UK construction industry in 2021-2022, 2022-2023, 2023-2024, and 2024-2025 and had CIS deducted in each year, all four years can potentially be reclaimed simultaneously. For a tradesperson with significant UK earnings, this can be a very substantial cumulative refund.
Using an Accountant
The combination of UK self-assessment, Irish Form 11, CIS reclaims, DTA credits, and expense documentation makes CIS reclaims more complex than a standard Irish tax return. Using an accountant who understands both systems ensures the claim is complete, the expenses are correctly calculated, and the Irish return correctly reflects the UK earnings and credits.
The accountant’s fee for this work is itself a deductible expense - on the UK return as a cost of the UK work, and on the Irish return as part of accountancy costs.
Paddy Malone FCA AITI
Paddy is the principal of Malone & Co. Chartered Accountants in Dundalk. A Fellow of Chartered Accountants Ireland and a Chartered Tax Consultant with the Irish Tax Institute, he has been advising businesses across County Louth and the North-East for over 35 years.