When you add lead time to a task, work on that task overlaps work on its predecessor. When you add lag time, you delay the start time of the successor task. Before you can start adding lead or lag time, you need to create a dependency between the two tasks.
Here’s how lead time looks in a Gantt chart:
To add lead or lag time:
Double-click a task name, and then click the Predecessors tab in the Task Information box.
In the Lag column, type the lead time or lag time you want.
To add lead time, type a negative number or a negative percentage (for example, -50%).
Lead time is an overlap between two tasks, where those two tasks share a dependency (a relationship between tasks). For example, if you want the second task to start even though the first task is only half complete, create a finish-to-start dependency between the two tasks, and then add a lead time of 50 percent for the second task.
To add lag time, type a positive number or percentage (for example, 2d).
Lag time creates a delay between two tasks that share a dependency. For example, if you want a 2 day delay between the end of the first task and the start of the second, create a finish-to-start dependency between the two tasks, and then add 2 days of lag time before the start of the second task.