Checks will be needed on some goods entering Northern Ireland from the rest of the UK as part of Brexit but bureaucracy will be kept to a "minimum", the government has said.
The government on Wednesday published proposals on implementing Northern Ireland provisions in the EU Withdrawal Agreement designed to keep trade in agricultural and manufactured goods aligned with that of the Republic of Ireland.
Some infrastructure screening animal and food products at ports will be "expanded".
First Minister Arlene Foster welcomed the "clarity" from Westminster, but added: "Obviously I didn't like the protocol at all but we have to make sure we minimise it as much as possible.
"I'm very pleased to see it talks about the unfettered access from Northern Ireland into the rest of the UK market.
"There won't be any tariffs paid on goods that are moving between parts of the UK, there won't be any new customs infrastructure, that is good news as well. And that, of course, we'll benefit from any new trade deals."
Deputy First Minister Michelle O'Neill also welcomed the clarity provided in the paper as "helpful".
"I think that the EU will assess for themselves justifications that have been published by the British Government and then have to decide whether they're satisfied," she told Stormont's Executive committee.
"The report has just been published so we're going to read through it, but it confirms the British Government will be seeking to put in place border control posts at ports of entry for all categories of agri-food that are coming from Britain and elsewhere from outside the EU, so that's what the Executive is now going to have to engage on."
Northern Ireland will have to follow EU rules on agriculture and manufactured goods, ensuring access to its single market and keeping the border with the Republic free-flowing in a key concession maintaining a decades-old peace. Screening will be supported by electronic processes, the Cabinet Office added, once the transition period finishes at the end of this year.
Michael Gove, minister in charge of Brexit preparations, said: "Our proposals will deliver unfettered access for Northern Ireland businesses to the whole of the UK market; ensure there are no tariffs on goods remaining within the UK customs territory; discharge our obligations without the need for any new customs infrastructure in Northern Ireland and, finally, guarantee that Northern Ireland businesses benefit from the lower tariffs we deliver through our new free trade agreements with third countries."
The EU wants to avoid Northern Ireland being used as a back-door entry point to its market and has pressed for controls.
The UK's position paper said there will be some limited additional process surrounding goods arriving in Northern Ireland, using "all flexibilities and discretion". It physically checks under 1% of third country movements notified through customs declarations and the government said in this case the risk would not be as high.
Using "sophisticated" data on trade flows for goods entering Northern Ireland, it would work with Irish authorities to tackle smuggling with new technology.
There will be no new physical customs infrastructure but some existing entry points for agri-food goods will "expand" to provide for "proportionate" additional controls. The government will maintain existing facilities at Belfast Port, Belfast International Airport, Belfast City Airport and Warrenpoint Port.
Northern Ireland goods sales to Great Britain are worth £8.1bn, with purchases worth £10.5bn. Together that trade comprises 56% of the country's total external trade in goods.
There will be no tariffs on goods remaining within the UK customs territory under the position adopted by Britain for negotiation with the EU.
Businesses in Northern Ireland will have "unfettered" access to sell to the rest of the UK market under the plan.
What the protocol does not do, it says, "is create - nor does it include any provision for creating - any kind of international border in the Irish Sea between Great Britain and Northern Ireland".
"That means its provisions must entail the minimum possible bureaucratic consequences for business and traders, particularly those carrying out their affairs entirely within the UK customs territory," it adds.
The UK Government has published proposals on implementing Northern Ireland provisions in the EU Withdrawal Agreement designed to keep trade in agricultural and manufactured goods aligned with that of the Republic of Ireland’s.