Northern Ireland teachers will predict the grades they think their pupils would have achieved in cancelled GCSE, AS and A-level exams.
A-Level and GCSE students will receive a calculated grade based on predictions from their teachers as well as statistics from previous performance, as will AS Level students, but it will not count towards their A-Level in 2021.
It marks a major change as AS Level results usually make up 40% of an A-Level mark.
Schools in Northern Ireland closed on March 20 in an attempt to halt the spread of the coronavirus. There is little prospect of them returning before September.
Education Minister Peter Weir made the announcement on grading while addressing the Stormont Assembly's Covid-19 Committee on Thursday afternoon.
Grades will be awarded for GCSEs due to complete in 2020 affecting, mostly Year 12 pupils, but not for GCSE units where GCSEs are due to complete in 2021, mostly affecting Year 11s.
In that case, pupils will have the option to take any outstanding units in 2021 and have missing components calculated using statistical modelling and/or to sit all units in 2021 and be awarded the higher grade from either option
These measures apply to students taking examinations set by the Council for the Curriculum, Examinations & Assessment (CCEA) which provides the majority of examinations in Northern Ireland, 87% of A-Levels and 98% of GCSEs.
Northern Ireland exams board CCEA will compare GCSE and A-Level results to take account of the fact schools may take a different approach to marking.
They will also develop an appeals process for pupils who are unhappy with their results.
Pupils will not be not be able to take re-sits in the autumn, but they can choose to take re-sits in the summer of 2021. The issuing of results will be aligned with England and Wales.
Mr Weir said that officials were also working closely with colleagues in the Department for the Economy on arrangements for vocational qualifications. Details will be announced by the Economy Minister as soon as it has been completed.
The Education Minister said that his priority was ensuring pupils receive fair results and that they "reflect their hard work and enable judgements to be made about their future progression to study or employment or other avenues".
“CCEA, the local examinations body, together with officials from my departments and others in the education sector have been working tirelessly to develop an alternative process," he told the committee.
“This is a very complex process and there is still more work to be completed, however, it is vital that pupils and their families receive some clarity on this issue.”
CCEA Chief Executive Justin Edwards said the exam board are "confident that the Summer 2020 exam cohort will achieve grades matching their expectations and that their future plans will continue unimpeded".
"We understand that this has been a very unsettling and challenging period for students and their families," he said.
"The details published today aim to give clarity and direction in previously unchartered waters and it is our aim to provide as much reassurance as possible that no student will be disadvantaged in these unprecedented circumstances."