Some €1.7m in university fees were undercharged due to an administrative oversight at Trinity College Dublin (TCD).

The university is now looking to recover the monies.

Just over 500 students were undercharged registration fees over the past three years - with some students now owing the university as much as €9,000.

The oversight affects those who applied for a Student Universal Support Ireland grant, or SUSI.

They were not approved for the grant, but were mistakenly charged lower fees by TCD as if they had been.

In a statement to Newstalk.com, TCD said it is writing to students and former students who applied for grants but were refused.

If a student believes that they will get a grant, they can enter college or progress to the following year by noting that they have applied of the grant.

If SUSI later refuses the grant, the student is informed and must then pay the fees themselves.

"It can sometimes take a long time for these decisions to be reconciled with the university's student record system," the university said.

"For the past three years, the college has mistakenly believed it was owed money by SUSI.

"In fact, the money was owed by individual students and that money is now being recouped."

It added that around 80% of students owe €3,000 or less - but a "small number" are being asked to pay up to €9,000.

"Naturally, this will pose difficulties and the college has put an interest-free payments system in place to help students who cannot pay their fees immediately."

"We recognise that this will cause difficulties for some students but in the interests of fairness to the vast majority of students who pay their fees on time and in full, the university will be pursuing unpaid fees in the normal way."

SUSI processed more than 103,000 applications in 2017 - with over 81,000 students awarded a grant for the 2017/2018 academic year.