"That [letter] is fraud," spokesperson Elijah Mhlanga told News24 on Thursday morning.
He said the department had made no such announcement.
Hubert Mathanzima Mweli is however the director general of the department.
The fake letter said: "Due to reports of the premature circulation of the Core Mathematics Paper 2 all National Senior Certificate Candidates having written the paper on the 2nd of November this year are to re-write the subject on Monday, 30 November 2015 from 09:00 to 12:00."