Avoiding check points or any other physical infrastructure on the Irish border is the UK Government's number one priority when negotiating post-Brexit arrangements for its only land frontier with the EU, a Whitehall position paper will state.
The document outlining the Department for Exiting the European Union's aims in talks with Brussels will also suggest there may be no customs implications at all on the Irish border if the UK and EU can strike an ambitious future partnership.
The Government paper will again dismiss any suggestion a customs border could be shifted to the Irish Sea, with checks and tariffs only in operation at entry and exit points between the island of Ireland and Great Britain.
Creating such a barrier between Northern Ireland and the rest of the UK was "not constitutionally or economically viable", it will state.
A Government source said: "Both sides needs to show flexibility and imagination when it comes to the border issue in Northern Ireland and that is exactly what our latest position paper will do.
"As Michel Barnier (EU chief negotiator) himself has said, the solution cannot be based on a precedent so we're looking forward to seeing the EU's position paper on Ireland.
"But it's right that as we shape the unprecedented model, we have some very clear principles. Top of our list is to agree upfront no physical border infrastructure -- that would mean a return to the border posts of the past and is completely unacceptable to the UK."
The document setting out the Government's negotiating principles for the border is being published 24 hours after the release of its position paper on the UK's long term customs arrangement with the 27 member bloc.
The two issues are intrinsically linked, with the dynamic at the border dependent on the shape of future customs relations between the UK and EU.
Tuesday's paper proposed a time limited-transition period of around two years. It then fleshed out two potential options for a long-term deal.
The more ambitious one would see the UK aligning or mirroring its customs approach with the EU model.
In that scenario, Wednesday's position paper on the Irish border will argue there would be no need for a customs border at all between the UK and Ireland.
The second proposed customs model, dubbed the "highly streamlined" approach, would see the UK negotiate agreements with the EU to reduce trade barriers and harness technology to avoid long queues at ports.
In the Irish context, the Government will say that arrangement could include:
:: A continued waiver on submitting entry/exit declarations;
:: Retaining membership of the Common Transit Convention to make it easier for Northern Ireland and Irish companies to transit goods;
:: New "trusted trader arrangements" for larger traders;
:: Cross-border trade exemptions that would mean no new customs processes at all for smaller traders. At the moment in excess of 80% of cross-border trade is done by small and medium sized enterprises.
The paper will also reaffirm the UK government's stated commitment to maintain the almost century-old Common Travel Area (CTA), which allows for free movement of UK and Irish citizens around the island.
It will also include a commitment to uphold the 1998 Good Friday Agreement in "all its parts" - sections of the historic peace accord are underpinned by EU human rights legislation.
The Government source added: "Our paper sets out some creative options on customs and shows the priority we place on making progress on this.
"Protecting trade is vital for the UK and Ireland -- in 2015 Northern Ireland sold £10.7bn of goods to Great Britain and a further £2.7bn to Ireland, while last year Great Britain exported £13.6bn worth of goods to Ireland, and imported £9.1bn -- so we're prioritising finding a solution that protects businesses' ability to access these important markets."