Cross-border trade in Ireland: A pricier pint
Guinness is one of many businesses that could be hit by a harder boarder.
It might just be Ireland's most famous product.
And indeed, the Guinness that is brewed at the St James's Gate brewery in Dublin is shipped to Europe and across the Atlantic.
But first the stout is transported north, in tankers that have become known as “silver bullets”, to be canned and bottled in east Belfast before returning to Dublin for export.
Diageo, the multinational company that owns Guinness, says that its silver bullets make some 13,000 border crossings a year.
The company estimates that even a short delay of 30 minutes to an hour for customs checks would add about 100 euros($115) to the expense of each trip, costing it some 1.3m euros a year.
If that happened, the price of Guinness might have to rise.
Guinness is not alone.
The abolition of customs controls in 1993 and of security checks after the Good Friday Agreement in 1998 has led to the creation of what is in effect an all-island economy, with supply chains criss-crossing the border.
Bilateral trade between Ireland and the United Kingdom is now worth over 1bn euros a week.
Most of that trade goes over the Irish Sea, but a fair amount crosses the border with Northern Ireland, especially in the agri-food sector.