What could be reasons for not accomplishing assigned work as per deadlines?

Is the team involved in the estimation process?

I'm looking forward to seeing the answer to Denise's question. One of my greatest irritants as a PM is watching a Manager or anyone else not performing the actual work (and who usually has never performed the work) make authoritative pronouncements of how long the work 'should' take.

I had a similar thought to Sergio. Estimations are just that, estimations. Also, you mention scope management. If no CR's are created, how are the changes analyzed, estimated, approved, etc? Scope creep will certainly break the estimations and schedule.

Sometimes team members are experiencing some personal or work problems and difficulties that would affect their performance and subsequently progressing their task inefficiently and not as planned. The project manager needs to continually monitor the performing team and communicate frequently with them trying to address any issues and try to help solving their problems if possible.

Thanks Sonali for sharing real time problem.
According to me, below could be the possible things.

1. If estimations are absolutely correct then, Is there any technology constraint to developers?
If yes then switch competent resource into the team.
If not then this must be either task understanding issue or efficiency issue.
2. As per your comments, if poor impact analysis is biggest reason, then there must be communication gap in team and lack of responsibility.
You can implement RACI in your team.
R - Responsibility
A- Accountability
C- Consult
I - Inform
3. Please review with team if there is any pre-negativity developed about project? - You can have a short meeting with each individuals.
4. It may be because of given time is less than expected time to accomplish task.
5. Does team working with pre-developed code / existing code from other team members or provider?
6. May be their maximum time is going to resolve bugs if any.

This could be some problems if team is not performing according to given timelines.

Hope this helps.

Hi Eric, the team is involved in estimation. I also tried re-validating the estimates with the team as I have seen work is expanding. But, team is sure that the estimates are correct and still not able to finish the work as per the estimation.