Leaving Cert students who wish to receive calculated grades are being urged to apply before tonight's deadline.
Registration closes at 10pm, with 10,000 yet to sign up.
Ciara Fanning, president of the Irish Second Level Students' Union, says anyone who wants a result this year needs to register.
She says: "Anyone who is a Leaving Cert student, so be it the Leaving Cert established, LCVP or Leaving Cert Applied must set up an account on the Leaving Cert Portal.
"Regardless of whether or not you want to opt for calculated grades. You need to sign up on the portal to make sure you receive a Leaving Cert result in 2020."
Yesterday as of Wednesday afternoon, the majority of Leaving Certificate students have registered for the new calculated grades system.
Some 48,075 students have signed up so far, and they have until 10pm on Thursday to apply.
Students can opt to sit the exam at a later date, but this has yet to be confirmed by the Government and it would not be in time for college admissions in September.
The calculated grades system will involve teachers assessing what grade they think a student would have received if they had sat the Leaving Cert examination.