The board made this known on Wednesday in a statement by its Head of Media and Publicity, Dr Fabian Benjamin.
According to Benjamin, the mock examination will hold on April 1, nationwide, contrary to its earlier announcement that the exercise will hold on March 23.
The JAMB spokesman said that the change was due to certain circumstances beyond the boards control.
He, however, urged candidates, who had indicated interest in the mock examination at the point of registration and had since printed the notification slips, not to bother printing another one.
All the details on the slips remain the same except the examination date, which is now April 1, 2019.
However, candidates are to begin the printing of the 2019 UTME notification slips from Tue., April 2.
All candidates, who registered for the 2019 UTME are to ensure that they print their examination notification slips before the day of the examination as no excuses will be entertained.
The public should note that the board will not reschedule examination for any candidate.
Candidates can print their slips anywhere, he stated.
Benjamin noted that 41,063 candidates created profiles and procured either UTME or Direct Entry (DE) ePINS, but were unable to complete registration after initiating the process as at the close of sale of UTME forms on Thur., Feb. 2 and subsequent close of registration.
He, however, said that it was in view of this that the board opened the registration portal effective on Wed., March 13 to enable all the candidates with either UTME or DE ePINS to complete the registration formalities.
The JAMB spokesman said: The portal will be closed on Friday, March 15 by 12 midnight.
This opportunity is for only candidates who had created profile and procured UTME or DE ePINS before the close of registration portal as the sale of ePINS has since been closed.
Please endeavour to register before Friday midnight if you are holding any of the ePINS for either UTME or DE.