Before Completion, a compensation event is notified under Clause 61.1 and the instruction is put into effect.
The quotation is accepted post Completion and therefore after half of the retention has been released.
Is 2.5% retention applied to the value of this CE at the next assessment date?
After Completion only half of the retention percentage can be retained on any assessments, right up until the Defect Date at which point it will all be released.
If your retention amount in CD part 1 is 5% then yes 2.5% would be withheld until Defect Date.