Cross-Border VAT: The Rules Irish and Northern Irish Businesses Keep Getting Wrong

The VAT treatment of trade between the Republic of Ireland and Northern Ireland is one of the most genuinely complex areas of Irish and UK tax following Brexit — and it is one where businesses on both sides of the border are regularly making expensive mistakes. It features prominently across our cross-border business guides for good reason.

Before 31 January 2020, the position was straightforward. Both jurisdictions were in the EU, both operated the same VAT framework, and goods and services moved between them under the EU internal market rules without customs procedures or separate VAT documentation beyond the intra-EU VIES reporting system.

Post-Brexit, the position is fundamentally different — though the Windsor Framework (and the Northern Ireland Protocol that preceded it) created a specific regime for Northern Ireland that distinguishes it from the rest of the United Kingdom. Understanding what that means in practice is essential for any business trading across the border.

The Windsor Framework: Northern Ireland’s Unique Position

Under the Windsor Framework (which replaced the Northern Ireland Protocol as the governing arrangement for NI’s post-Brexit status), Northern Ireland occupies a unique position in the global trading framework. For goods, Northern Ireland remains aligned with EU single market rules — meaning goods moving between the Republic of Ireland and Northern Ireland continue to be treated as intra-EU movements for VAT and customs purposes. For services, Northern Ireland is treated as part of the UK.

This distinction between goods and services is the most important structural feature of the NI VAT position, and it is the source of considerable confusion. We explore the practical implications of the Windsor Framework in more detail in our guide to cross-border VAT under the Windsor Framework.

For goods moving between ROI and NI: The EU VAT rules apply. An ROI business supplying goods to an NI business (where both are VAT registered) uses the zero-rating for intra-EU supplies — the supply is zero-rated in the Republic, and the NI buyer accounts for acquisition tax under the reverse charge mechanism. This is essentially the same as it was before Brexit.

For services supplied between ROI and NI: The UK is treated as a third country. Services supplied by an ROI business to an NI business are governed by the UK-EU place of supply rules and the general B2B rule — the place of supply is where the customer belongs (the UK, i.e., Northern Ireland), and the ROI supplier zero-rates the supply while the NI recipient accounts for UK VAT under the reverse charge.

The practical outcome in many cases is similar — zero rating for the supplier, reverse charge for the recipient — but the legal framework is different, and some categories of supply are treated differently under EU rules than under UK rules.

The Most Common Mistakes

Treating goods and services the same. The goods/services distinction under the Windsor Framework means you cannot apply the same VAT logic to a supply of physical goods and a supply of consultancy services just because both are going to the same NI customer. The rules are different, and applying the goods rule to a services supply (or vice versa) will produce the wrong VAT treatment.

Not registering for UK VAT when required. An ROI business that makes taxable supplies of goods or services in the UK above the UK VAT registration threshold (currently £90,000 per year) may be required to register for UK VAT. This is particularly relevant for businesses that supply digital services, certain professional services, or physical goods directly to UK consumers (as distinct from B2B supplies to VAT-registered UK businesses).

The “overseas seller” rules for UK VAT require non-UK sellers to account for UK VAT on B2C supplies above the threshold. If you are selling products or digital services to consumers in Northern Ireland (or anywhere in the UK) and your total UK B2C turnover exceeds the threshold, you should be registered for UK VAT and accounting for UK VAT on those sales.

Incorrectly zero-rating B2C goods sales to NI. Under pre-Brexit rules, Irish VAT was charged on goods sold to consumers in Northern Ireland (as the goods were moving within the EU, the supply was subject to Irish VAT until certain distance selling thresholds were reached). Post-Brexit, the Windsor Framework’s treatment of goods under EU rules means the VAT position on consumer goods sales to NI requires specific analysis — it is not as straightforward as either the old EU rules or the standard UK rules.

Not retaining evidence for zero-rated intra-EU supplies. Where goods moving from the Republic to Northern Ireland are zero-rated as intra-EU supplies, Revenue requires the exporter to hold commercial evidence that the goods left the Republic and arrived in Northern Ireland. Transport documentation, delivery notes, and customer acknowledgment are part of this evidence chain. Without it, Revenue can challenge the zero-rating and assess the supplier for the Irish VAT that should have been charged.

IOSS and OSS complications. The EU’s Import One Stop Shop (IOSS) and One Stop Shop (OSS) schemes simplify VAT compliance for e-commerce businesses selling to EU consumers from outside the EU. If you are an ROI business selling goods to consumers in EU member states, OSS may be relevant. If you are also selling to NI consumers, those sales fall under UK rules. Running both EU OSS and UK VAT registrations simultaneously adds complexity that many small e-commerce businesses have not planned for.

The Practical Checklist for Border Businesses

If you are an ROI business trading with Northern Ireland customers, or an NI business trading with ROI customers, work through the following questions:

Are you supplying goods, services, or both? The VAT treatment differs and you need to be clear on the distinction for each transaction type.

Are your customers VAT-registered businesses or unregistered consumers? B2B supplies to VAT-registered customers generally involve reverse charge mechanisms and zero-rating. B2C supplies to unregistered consumers are more complex and the VAT liability may rest with the supplier.

Have you assessed whether you are required to register for VAT in the other jurisdiction? The UK registration threshold for overseas sellers is £90,000 of UK taxable supplies. The Irish registration threshold is €40,000 for services and €80,000 for goods.

Are you retaining the correct evidence for zero-rated cross-border supplies? Both Revenue and HMRC can challenge zero-rating without adequate documentary evidence.

Is your accounting system correctly treating NI transactions under the appropriate rules? Many accounting software packages have been updated post-Brexit but the configurations can be complex — particularly for businesses with mixed goods and services supplies to NI customers.

The Northern Ireland Customs Complexity

For businesses physically moving goods between the Republic of Ireland and Great Britain (not Northern Ireland — Great Britain is England, Scotland, and Wales), full customs procedures apply. An ROI business importing goods from a GB supplier, or exporting to a GB customer, faces import duties, customs declarations, and potentially different VAT rules.

Northern Ireland’s unique position under the Windsor Framework means it is treated differently from GB for these purposes — but only in relation to goods. The practical consequence is that many Dundalk businesses that trade with both NI and GB customers need different documentation and VAT treatments for what superficially look like similar “UK” transactions.

This is one of the lasting legacy complexities of Brexit for the border region, and it shows no signs of simplifying. If you are considering setting up a business that operates on both sides of the border, the VAT structuring decision is one of the first things to get right. If your business has grown to include cross-border trade since 2020 and you have not had a formal review of the VAT and customs treatment of those transactions, that review is overdue.