With all the Brexit uncertainty in particular if there is a No Deal by the time the UK leaves the EU on the 29th March 2019 on area of concern are increased car hire costs in Ireland.
There are concerns in the insurance and travel industry about "Green Cards" for drivers taking their vehicles in and out of the UX and this includes Northern Ireland. I remember was back in the late 60s / early 70s before the UK joined what was the EEC - Common Market. I had to contact my insurance company for "insurance cover" to take my car to France and other continental European countries. A document printed on green paper was sent out by the insurance company.
I remember earlier family holidays with my late father getting these documents and it was very common, however in the 1960s and even early 1970s there was not the volume of vehicles crossing the channel as there is in 2019.
In Ireland many of these Green Card documents have been printed and templates sent to individual insurance companies. If the UK crashes out of the EU without a deal then anyone and this includes the thousands and thousands of trucks and other commercial visitors entering the UK will need a Green Card plus the UK registered vehicles going to mainland Europe and Republic of Ireland.
If you need to add an additional driver to your vehicle and contact your insurance company, in most cases your insurance company will make an administration charge for this. So if that insurance company is going to have to issue a Green Card then it is more than likely they will have to make an admin charge. With regards to commercial vehicle operators this charge is going to be passed onto the consumer most likely.
If an insurance company says they will absorb these admin charges, I reckon that when the annual vehicle insurance is up for renewal the premium will rise.
Getting back to the heading in this article, as Northern Ireland is part of the UK then owners of vehicles wanting to cross the border (however soft or hard) from the Republic into Northern Ireland or vica versa will need the appropriate insurance cover.
Someone who works in Northern Ireland, but lives in another county of Northern Ireland County Donegal for example which is in the Republic will need Green Card cover. The driver might cross the border a couple of times on his / her route to and from work.
At the moment when you hire a car in the Republic or Northern Ireland and want to take it over the border you will find that some car hire companies make an additional charge - often to do with breakdown rescue charges. (AA breakdown for an UK registered car travelling in the Republic could come under AA Europe via Calais in France for example).
Other car hire companies allow their vehicles to cross the border with no additional cost for the hirer. However look at the Green Card situation. If the hire car rental company has to have these and somewhere along the line they have to pay either in an administration charge to their insurance company or by higher premiums, they will have to pass on these costs and of course we know who will pay.....the person hiring the car.