The British government wants a time limit on its temporary customs plan to avoid a hard border with Ireland after Brexit.
A document published this afternoon says they expect a permanent solution to be in place by December 2021 - but there's no firm commitment.
The note was published after a series of meetings between the British Prime Minister Theresa May and Brexit Secretary David Davis.
The terms will be presented to the European Council later this month.
Sky's political editor, Faisal Islam, says it seems like a victory for the Brexit Secretary - who'd reportedly threatened to quit over the issue.
"What you have here is a compromise: a compromise that's clearly kept David Davis on board, a compromise that potentially can be put to the European Union for negotiation.
"But I'm not sure what Brexit-minded MPs will feel about this".
The EU chief Brexit negotiator has responded to the proposals on Twitter, saying there are three key questions that must be answered.
Michel Barnier says he will be looking to see if it provides a workable solution to avoid a hard border, while respecting the integrity of the Customs Union.
He added that while he welcomes publication of the proposal, it needs to be assessed to see if it is an 'all-weather backstop'.
I welcome publication of #UK proposal on customs aspects of IE/NI backstop.
We will examine it with 3 questions: is it a workable solution to avoid a hard border? Does it respect the integrity of the SM/CU? Is it an all-weather backstop?
— Michel Barnier (@MichelBarnier) June 7, 2018
While the Brexit coordinator at the European Parliament, Guy Verhofstadt , has said a "backstop that is temporary is not a backstop".
Difficult to see how UK proposal on customs aspects of IE/NI backstop will deliver a workable solution to avoid a hard border & respect integrity of the SM/CU. A backstop that is temporary is not a backstop, unless the definitive arrangement is the same as the backstop. #Brexit
— Guy Verhofstadt (@guyverhofstadt) June 7, 2018
The Tánaiste Simon Coveney has repeated that a legally-binding backstop is vital, and that a great deal of work "remains to be done".