Leaving Certificate students who want to do the exam in November will be sitting their papers in the evenings and weekend.
The Department of Education has published some details for the delayed sitting of the June tests, which will be held subject to public health advice.
Junior Cycle exams, for adult learners and early school leavers only, will also start in November.
The postponed Leaving Certificate, starting November 16, will be open to any 2020 candidate and may appeal to anyone who is unhappy with the calculated grades they receive.
It is impossible to predict what the uptake will be, as it will depend on how students feel after receiving their grades.
There are more than 30 Leaving Certificate subjects and normally the timetable extends over about three weeks.
However, in November, exams may not run in all subjects and will depend on whether there is demand from students for a particular subject.
There will be written exams only, with no orals or practicals.
Meanwhile, universities have sought urgent talks with the Department of Education to ensure the Leaving Certificate results and CAO offer season does not descend into the chaos seen in the UK.
As the results date of September 7 looms, the Irish Universities Association (IUA) wants a meeting with senior Department officials to secure assurances that their calculated grades plan will hold up.
The move by the university registrars comes on the heels of concerns expressed by Professor Pól Ó Dochartaigh of NUI Galway.
He warned that blanket grade inflation of Leaving Cert results must be avoided.
Registrars are responsible for college admissions and are seeking guarantees from the Department.
This year, the June exams were replaced with a system where teachers provided estimated marks and class rankings for pupils in each subject.
These are now going through a series of checks to yield the final calculated grades.
Similar processes in the UK sparked a furore when it emerged marks awarded by teachers to disadvantaged students were disproportionately marked down.
One of the worries of the IUA is timing, with colleges already concerned the start of the academic year has been pushed back.
The registrars want certainty that the results issued on September 7 will be the "final and definitive" set of grades.
CAO Round 1 offers will follow on September 11, and most colleges are starting the term on September 28.