State Education Minister Rob Stokes said that NESA would not receive additional funding to correct the mistake.
"I understand it was an administrative error within the organisation," he told Triple M.
"Our students show incredible diligence when undertaking their HSC exams, and expect the independent authority charged with administering those exams to demonstrate the same level of care and excellence."
Stokes said that the incorrect dates would not affect the certificates' validity.
NSW shadow education minister Jihad Dib slammed the government over the mistake.
“We asked 70 000 HSC students to give their best last year. What do what they get in return? A Gov that can’t even get the year on the official HSC Certificate correct. They are right to feel disappointed and let down,” he wrote on Twitter.
Mix94.5 reports that Dib went on to criticise the government further.
"How can they and their achievements not count with this government?” he said.
“This government can’t make right the sense of disappointment and neglect but they can reissue properly valid certificates.”
The certificates were dated 2017 rather than 2018.