Jamb portal

The JAMB Change of Institution form is currently available for purchase and can be accessed through JAMB profile or authorized CBT centers, with no fixed closing date as it remains open until the end of the admission year, though certain schools may halt changes once their post-UTME forms are on sale.

This is the answer to your question: Is JAMB's change of institutions on or has it started/opened? Some candidates who seem to know that the form is on are asking to know the closing date. 

Now that the JAMB results are out or even before the release of the results, candidates want to consider the change of institutions.

But in most cases, you had better wait till you know your fate in the UTME result. See How to Check JAMB Results With 4 Methods (Including the Original UTME Result).

If for one reason or the other, you think you must change institutions, you may want to know if the form has opened or the closing date so you can know, to what extent you need to wait before you effect the changes.