Edexcel finished marking its papers at least 10 days ago, helped partly, it says, by efficiency gains made from increasing its use of technology.
Ken Boston, the exam regulator, backed the early release of grades to students.
However, the Department for Education and Skills is believed to have overruled the move.
It feared that students taking all their A-levels through Edexcel might gain an advantage in university applications over those sitting exams with other boards.
Ministers are understood to be concerned about approving the early release with other changes in the air which could affect the timing of results and university applications, for example moves toward a six-term year.
These changes include the electronic marking of GCSE and A-level scripts - trialled by two of England's three boards this year - which will be expanded. Scripts are scanned by computer and then sent electronically to examiners for marking.
Edexcel marked more than a million A-level, GCSE and vocational papers on-screen this year and the AQA board carried out a smaller trial. Although controversial, the trials were judged successful by the Qualifications and Curriculum Authority and more papers will be marked electronically next year.
Even among exams that will continue to be marked traditionally next year, there are likely to be changes in the way scripts are sent to examiners.
Currently, many schools use the Royal Mail to send out pupils' answers for marking. This year, the National Assessment Agency, a division of the QCA, carried out an experiment in which GCSE and A-level scripts from 50 schools and colleges in Leeds were sent by courier.
Although a formal evaluation has yet to be carried out, Dr Boston says that the trial has been a success and could be expanded nationwide in coming years.