You can handle undone user stories in different ways. Decide what you want to do with undone items and take the action while completing a sprint. Yodiz gives you an option to copy or move these items at the completion of a sprint. If you have some incomplete items in a sprint, Select from following 3 actions for UnDone items:

• Move to Sprint: to move undone items to another sprint
• Copy to Sprint: to keep current sprint contents intact and duplicate UnDone items to target sprint. You have the option to copy only undone items or all items.
• Move to Backlog: to move Undone items back to Backlog

Yodiz Tip: Use reports module and create a custom report to keep the history of a sprint, if you need.