If there are price changes within the last 5 minutes of a reverse auction, the clock will reset to 5 minutes. This will continue until there are no more price changes for a 5 minute period.
There is no ability to extend an auction that has ended. However, you can Reopen a Request after an auction has ended (and after the Proposals Due By Date has passed).
If you choose to reopen a Request, you can keep the Request open to proposals and view new proposals or revised prices in the Comparator screen. You can notify firms in the Comments channel, or via a Clarification, if you wish to place a time limit on how long you will consider new proposals.
If you wish to conduct a new reverse auction you can Copy the Request and select Enable Reverse Auction while it is still a draft.