Tax for UK Nationals in Ireland: Cross-Border Work, ISAs and What You're Owed

The Common Travel Area: what it does and doesn't do

It gives you the right to live and work here without a permit. It does nothing at all for your tax position.

Irish tax residence is decided by days: 183 or more in a tax year, or 280 across the current and previous year provided you were here more than 30 days in the current one. Citizenship isn't part of the test. You get the same credits, rate bands and reliefs as an Irish citizen — and the same obligation to claim them yourself, because none apply automatically. Revenue's rules are on its tax residence page.

The habit that costs UK arrivals most: there is no P800 here. HMRC calculates overpayments and writes to you. Revenue does not. Ireland deducts PAYE in real time and then stops. If you're owed money, you have four years to ask, and nobody will prompt you.

Trans-border Workers Relief

If you live in Ireland and work full-time across the border — or anywhere abroad you commute to — this is the most valuable thing on this page.

Trans-border Workers Relief (section 825A TCA 1997) exists because someone resident in Ireland is taxable here on worldwide income, including a salary already taxed in Northern Ireland. A foreign tax credit helps, but if Irish tax on the euro-equivalent salary exceeds the UK tax paid, you'd face a top-up bill. This relief removes it.

The conditions:

• You're Irish tax resident.
• The employment is exercised wholly outside the State, apart from duties that are merely incidental.
• It's in a country with which Ireland has a double taxation agreement — the UK qualifies, under the 1976 convention.
• The employment is held for a continuous period of at least 13 weeks in the tax year.
• The foreign tax is actually paid and not refundable.
• For every week you work abroad, you're present in the State for at least one day in that week.
• A proprietary director cannot claim it in respect of a connected company.

How the relief is calculated. Your Irish liability is reduced to a "specified amount":

Total Irish tax liability × (income other than the foreign employment income ÷ total income)

Your Irish bill drops from €11,200 to €1,866.67 — effectively, you pay Irish tax only on the proportion of your income that isn't the cross-border salary.

And if the rental income didn't exist? The specified amount would be zero. With no other Irish-source income, a qualifying cross-border worker pays no additional Irish income tax on that salary at all.

One more benefit that's easy to miss: USC does not apply to Northern Ireland employment income that qualifies for this relief.

You claim it by filing an Irish return — you're generally within self-assessment as a cross-border worker, which means an annual return declaring worldwide income regardless.

The hybrid working trap

This one is current, and it's catching people right now.

The relief requires the employment to be exercised wholly outside the State, apart from incidental duties. If you're Irish-resident and you regularly perform substantive work from your home in Donegal, Louth or Monaghan, those duties are no longer being exercised wholly outside Ireland — and the relief can be lost entirely.

Revenue's Covid-era concession for home working has ended and should not be relied on for current arrangements. A working pattern that was fine in 2021 may not qualify now.

If the relief doesn't apply, you fall back on ordinary double tax relief — a credit for UK tax paid, which can leave an Irish top-up. On the figures above, that's the difference between €1,866.67 and something much closer to €11,200. Two days a week at the kitchen table can be an expensive habit.

There's also a payroll dimension: if you perform employment duties in the Republic, Irish PAYE, USC and PRSI may need to be considered for those workdays, which is your employer's problem as well as yours. Worth raising with them before Revenue raises it.

Your ISA doesn't stay tax-free

The tax-free status of an ISA is a feature of UK law. It does not travel.

Once you're Irish tax resident, Ireland applies its own rules to the income and gains inside that wrapper, and Ireland has a distinct regime for foreign investment products that can be less favourable than ordinary capital gains treatment. Exactly how yours is treated depends on what it holds and how it's structured — a cash ISA, a stocks and shares ISA and a Lifetime ISA are not the same question.

The same logic applies to Premium Bonds, and to any UK product whose appeal was its UK tax wrapper.

This is not a disaster if handled deliberately, and it is a genuine problem if left on autopilot for four years while it quietly accumulates untaxed income. If you have UK investment products, get the position established rather than assumed — that's what our VIP Premium service is for.

UK pensions and National Insurance

Your NI record isn't lost. Contribution periods completed in the UK and PRSI contributions in Ireland can both count towards your eventual State Pension position, and there are arrangements for taking foreign contributions into account. Your UK NI record is also worth checking for gaps while you can still do something about them.

UK workplace pensions and SIPPs continue to exist, but the tax treatment of contributions and eventual drawdown becomes a two-country question once you're Irish resident. Contributions to a foreign scheme don't automatically attract Irish relief — that depends on the scheme type, any relevant treaty provision, and your circumstances.

Meanwhile, on the Irish side, pension contributions are the largest relief available to a higher earner: relief at your marginal rate on contributions up to an age-related percentage of earnings, capped at €115,000 of earnings. A €5,000 contribution at the higher rate costs you €3,000. See AVC and pension tax relief.

If you kept property in the UK

Very common, and it has two sides.

Rental income. If you're Irish tax resident, UK rental profit can be within the Irish net as well as the UK one. The 1976 convention and a foreign tax credit prevent double taxation on the same profit, but the credit must be claimed and evidenced, and it's capped at the Irish tax attributable to that income.

Selling it. After three consecutive years of Irish residence you become ordinarily resident here from the start of year four, which brings disposals of assets wherever located within Irish CGT at 33% — including a flat in Manchester. UK CGT rates on residential property and Irish CGT are not the same, so expect the credit to cover only part of the Irish charge. Ordinary residence continues for three years after you stop being Irish resident, so moving back doesn't end it immediately.

Note too that the euro conversion matters: Irish CGT is computed in euro using values at acquisition and disposal, so sterling movement between those dates forms part of your Irish gain. The framework is in moving to Ireland: how cross-border taxes work.

What's unclaimed on the Irish side

• Your arrival year, usually the largest single refund — a full year's credits against a part year's earnings. Split Year Treatment protects it by excluding pre-arrival employment income; since the Finance Act 2024 you self-assess and claim it in your return.
• The Rent Tax Credit — up to €1,000 a year from 2024, €500 for 2022 and 2023, doubled for jointly assessed couples. See the Rent Tax Credit guide.
• Medical and dental expenses at 20% for the household. Non-routine dental needs a Form Med 2 from your dentist.
• Remote working relief, a deduction worth your marginal rate.
• Joint assessment, if your spouse earns much less — it has to be elected, there's no automatic household treatment.

The full list is in the top Irish tax deductions you could be missing.

What you need before you claim

• Your PPSN and myAccount access.
• Your IBAN entered in your Revenue profile — refunds are paid by transfer only.
• Your Employment Detail Summary for each Irish year, from myAccount.
• Your P60 or P45 and UK payslips, if you're claiming Trans-border Workers Relief, plus evidence the UK tax was actually paid and not refunded.
• A record of your working pattern — which days you worked where. This is the evidence that decides whether the relief applies, and it is much easier to keep than to reconstruct.
• UK investment and ISA statements, showing holdings and income.
• UK rental accounts and evidence of UK tax paid.
• Your RT number and landlord details if you rent here.

If you'd rather have the whole position reviewed, our Tax Back service handles the Irish return. No refund, no fee.

Four years, and one deadline

You can claim back four Irish years. As of 2026 that's 2022, 2023, 2024 and 2025 — and 2022 closes permanently on 31 December 2026.

If you're moving back to the UK, do the review before you go, while you still have an Irish bank account and myAccount access. See leaving Ireland and the refund you might be owed.

Questions we get asked

I live in the South and work in the North. Do I really have to file an Irish return?

Yes. As an Irish resident you're taxable here on worldwide income and you're generally within self-assessment, so an annual return declaring worldwide income is required — even though your salary already had UK tax and National Insurance deducted at source. Trans-border Workers Relief is claimed on that return, so not filing means not claiming.

I've started working from home two days a week. Does that affect my relief?

Potentially yes, and significantly. The relief requires duties to be exercised wholly outside the State apart from incidental ones. Regular substantive work from an Irish home office can break that condition, and the Covid-era concession has ended. Get your specific pattern reviewed rather than assuming continuity.

Does my ISA stay tax-free now that I live in Ireland?

No, not automatically. Ireland doesn't recognise the UK wrapper and applies its own rules to foreign investment products, which can be less favourable than ordinary CGT treatment. What applies depends on what the ISA holds. This is worth resolving early rather than at year four.

Is there an Irish equivalent of the P800?

No, and this is the single most expensive assumption UK arrivals make. HMRC calculates your overpayment and contacts you; Revenue doesn't. You request a Statement of Liability and file a return yourself, within four years.

I live in the North and work in the South. Is there a relief for me?

Not on the UK side. Trans-border Workers Relief is an Irish relief for Irish residents. Northern Ireland residents working in the Republic declare that income to HMRC under self-assessment with a credit for Irish tax paid, and can face a UK top-up. That's a question for a UK adviser.

If you commute across the border, check one thing this week: whether Trans-border Workers Relief has ever been claimed on your Irish returns. On the figures above it's worth over €9,000 a year, and it is not applied automatically.

Related reading

• Moving to Ireland: how cross-border taxes work
• AVC and pension tax relief in Ireland
• Top Irish tax deductions 2026