Free movement of people between the EU and UK will end in March 2019, UK government ministers have said.
From that date EU workers moving to the UK will have to register, at least until a permanent post-Brexit immigration policy is put in place.
But Home Secretary Amber Rudd has sought to reassure business there will not be a "cliff edge" in terms of employing foreign workers after Brexit.
She said policy would be evidence-based and take into account economic impact.
The CBI said businesses "urgently" needed to know what EU migration would look like, both in any "transitional" period after March 2019 and beyond.
Immigration was one of the central topics of last year's EU referendum campaign, and ministers have promised to "take back control" of the UK's borders as they negotiate Brexit.
The UK is currently due to leave the EU at the end of March 2019, but there has been increasing talk of a "transitional" (or "implementation") stage of around two years to smooth the Brexit process.
Speaking on BBC Radio 4's Today programme, Home Office minister Brandon Lewis said details of how the government would manage immigration after Brexit would be revealed in a white paper later this year, and that the immigration bill would go through Parliament in 2018.
Mr Lewis said it was a "simple matter of fact" that EU free movement rules would not apply after 2019.
More detail of what would happen was later provided by the home secretary, with Ms Rudd, speaking during a visit to Troon, South Ayrshire, saying the "implementation phase" would involve new EU workers registering their details when they come to the UK.
She also said the government had promised an "extensive" consultation to listen to the views of businesses, unions and universities.
The Home Office has asked the Migration Advisory Committee to study the "economic and social costs and benefits of EU migration to the UK economy", its impact on competitiveness, and whether there would be benefits to focusing migration on high-skilled jobs. It is due to report back by September 2018 - six months before Brexit.
The home secretary said: "We will ensure we continue to attract those who benefit us economically, socially and culturally.
"But, at the same time, our new immigration system will give us control of the volume of people coming here - giving the public confidence we are applying our own rules on who we want to come to the UK and helping us to bring down net migration to sustainable levels."
Speaking in Sydney, Foreign Secretary Boris Johnson said he was unaware of the report that has been commissioned, adding that immigration had been "fantastic for the energy and dynamism of the economy" but "that doesn't mean that you can't control it".
For Labour, shadow home secretary Diane Abbott said there was "far too much heat and not enough light about immigration, so any truly objective and well-informed analysis must be welcome".
But she raised concerns about the timescale for the Migration Advisory Committee report: "Six months before Brexit will not be enough time to structure a new immigration system."
Lib Dem home affairs spokesman Sir Ed Davey said the move would "do nothing to reassure the hospitals that are already seeing record numbers of EU nurses leaving, or the companies struggling to recruit the staff they need".
"The NHS, businesses and universities that depend on European citizens need answers now, not in another 14 months' time," he added.
The CBI said commissioning the report was a "sensible first step", adding: "Workers from across Europe strengthen our businesses and help our public services run more smoothly - any new migration system should protect these benefits while restoring public confidence."
But the Labour MP Yvette Cooper, who chairs the Commons home affairs committee, said it was "staggering" that it had taken the government a year since the EU referendum to commission it.
And property developer Richard Tice, co-chairman of Leave Means Leave, told BBC Radio 4's World at One: "This commission should be reporting by this Christmas, not by next September. It's completely unacceptable for this to drag on ... the government needs to rapidly accelerate this."
Manufacturers' organisation EEF said the migration committee was "best placed" to advise on what EU migration should look like after Brexit.
Both EEF and the CBI called for an immediate resolution of the question of the status of EU nationals already living in the UK.