When sharing work on a task, how do we know how much time each of us has put in?

For a quick view of user-specific time input on a task - turn to the Time log.
Available on an open card - it brings quick insight into how much time different people have been working on a task. Individual Time Logs

Further information on this subject can be read form the Time Report.

Kanban Tool is a visual management solution that helps companies visualize workflow, track project progress, and analyze and significantly improve business processes. Kanban Tool provides powerful online Kanban boards with seamless time tracking and insightful analytics. Our Kanban software works perfectly in any business process and is designed for teams that want to visualize work on a Kanban board.