Decline a pull request when you don't want to merge the changes in that pull request in their current state. The pull request author or any reviewer can decline a pull request.
Declining a pull request can't be undone. Once you decline a pull request, you'll have to open a new pull request request to review code for the same branch.
Declining a pull request has no impact on the source or destination branches of the pull request. You can continue to comment on a declined pull request, but new changes pushed to the branch no longer update the pull request.
To decline a pull request, click the Decline button at the top right of the page. After the pull request is declined, the comments and tasks are preserved.
To see a list of declined pull requests, click Pull Requests in the sidebar of your repository. From the first dropdown next to Filter by, select Declined.