When is a Sprint over?

You should try to keep the sprints at a fixed length. It is always possible that the Product Backlog items you dedicated to at sprint planning do not fit the sprint length. It is possible that you discover that you have over committed or that you have under committed.

In both cases you should talk to your Product Owners and renegotiate the content of the increment.

> Isn't the Sprint over when there are no more tasks to be completed?

No, it just means that there is an opportunity to replan and perform further work until the Sprint time-box expires.

The priority should be given to any additional work that is needed to achieve the Sprint Goal. Assuming that the Goal has already been met, the team can instead:

- improve its efficiency, such as by cross-training or study
- improve the Definition of Done and/or the release potential of increments
- pay off any technical debt that may have been incurred
- perform additional Product Backlog refinement
- bring forward other work from the Product Backlog with the agreement of the Product Owner
- help the Scrum Master in performing his or her service to the organization, such as by assisting in agile adoption

Allow me to answer a little differently.....

Think of a timebox as a "max. amount of **time** allocated" for a checkpoint.

The level of effort that goes into what we do during this time is a separate consideration. i.e. As others have written above, sometimes all anticipated work is completed prior, and some may still be left.

If the team has completed all PBIs early, the remaining time can be used wisely doing one or more of the following: Refinement, Learning/training, paying technical debt, team building, discuss with PO and take an additional PBI only if it can be completed in this sprint and it aligns with the sprint goal.

Typically when all PBIs are completed early, there isn't much time left.

Agreed with Nitin ,its definition and agreed with others who say how can we utilized that remaining time by taking unanimous decision .

Thanks guys for the responses.

Or checking with PO if increment could be already shipped to customers

The best answer is 1 :When the time-box expires

Because all events in scrum they are time-boxed (have max time) it's an imported rule in Scrum .

- Some times all tasks completed before time-box ---> you have to improve your estimate on the next sprint  and  keep the sprint at a fixed length. 

"Scrum is founded on empirical process control theory "

"Three pillars uphold every implementation of empirical process control: transparency, inspection, and adaptation." 

NB:

When the time-box expires and When all tasks do not  completed ---> the Sprint over

When the time-box doesn't expires and When all tasks did not complete ---> the Sprint is not  over

When the time-box expires and When all tasks completed ---> the Sprint over (the best situation & Sprint Goal)