There is no fixed deadline for accepting or declining an offer of place. However, students applying for general bachelors' degrees should decide as soon as possible because they cannot proceed to course enrolment until after accepting the offer. Deadlines often apply to other phases in their enrolment.
Offers for places in specialised programmes may require that applicants decide by a specific date, after which any outstanding offers may lapse.
If you accept an offer you can still cancel your application later if necessary.