The Withdrawal Agreement Bill makes it clear that there will be more costs, more border checks and more uncertainty for Northern Irish companies trading with England, Scotland and Wales than with Ireland.

That is a consequence of the government's decision to agree to effectively erect a customs and regulatory border in the Irish Sea in order to avoid a land border on the island of Ireland.

The implications of the proposed deal, which would see Northern Ireland (NI) comply with EU customs regulations while legally being part of the UK customs area, are set out in an impact assessment attached to the bill set before parliament last night.

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The document is explicit that there will be extra costs and processes for businesses trading with Great Britain (GB), but none for deals with Ireland, which for practical purposes will be treated as intra-EU deals.

Just how much the hit to NI business will be is not clear.


The document repeatedly states that there is no data on the number of consignments that move between NI and GB every year, probably because there was not previously any need to know as they were not considered international trade.

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There is little question that it will be significant.

Trade in both directions between GB and NI accounts for 56% of all NI trade, with a total value of £18.1bn according to the most recent figures covering 2017.

Trade with Ireland meanwhile account for 16% of NI trade.

Almost one in five NI businesses exports goods to GB, and one in 20 imports from the rest of the UK.

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Of these, almost all have fewer than 50 employees, suggesting small companies will be the most seriously affected.

The assessment sets out that some declarations will be required for west-east trade, from NI to GB, a fact Brexit Secretary Stephen Barclay appeared not to understand when appearing at a House of Lords committee on Monday.

"Some practical information will need to be provided electronically on movement of goods West-East​," the assessment states.

Goods moving east-west from Great Britain to Northern Ireland meanwhile will be required to complete both import declarations and Entry Summary (ENS) Declarations, a pre-customs declaration, "because the UK will be applying the EU's Universal Customs Controls in Northern Ireland. This will result in additional administrative costs to businesses."

How much is not certain, but HRMC has estimated that each declaration will cost between £15 - £56, with greater costs falling on small and "micro" businesses that need to use third-party customs agents.

There will be extra costs too associated with the new system of tariffs, which will only apply to GB goods that may end up in Ireland, and subject to a complex system of rebates.

The assessment states: "Businesses in Great Britain may face familiarisation costs in adapting to paying some tariffs on the movement of their goods from Great Britain to Northern Ireland."

There will also be additional customs checks and documentation required at the Northern Ireland sea border for agricultural and food products sent from GB, requiring more infrastructure, more staff, and a minimum fee of €55, set by the EU, to cover the cost of any assignment.

Goods will also have to comply with the requirements of EU regulation and legislation.

The impact assessment is not complete but it may be all MPs have to go on as the Chancellor Sajid Javid has refused to commission a Treasury study, saying the benefits of the deal are "self-evident".

But it seems unarguable that the price of the UK being able to strike free-trade deals with countries around the world will be to place costs and barriers to commerce not just with the EU, but with Northern Ireland, one of the four nations of the Union.