A successor starting early can represent an intentional overlap or an unexplained date adjustment. Express the intended relationship first: must the next task wait a fixed interval, or may it overlap a proportion of its predecessor?

In Project desktop for Windows, create the dependency before adding an offset. Double-click the successor and open Task Information, Predecessors. Enter the offset in Lag: positive values delay and negative values create lead. Keep the dependency type visible, because the offset belongs to that relationship.

For this exercise, use finish-to-start links, automatically scheduled tasks, one common working calendar and no assigned resources or competing constraints. A percentage offset uses the predecessor's duration as its basis. This describes planned timing; it is not a measurement that a deliverable is ready for handover.

Compare two different rules

Give a fictional Draft task four working days. In one copy, set the Review dependency to a one-day lag, entered as 1d. In another, use a 25% lead, entered as -25%. The former means a wait after Draft; the latter represents one working day of overlap under the stated simple calendar.

Extend Draft to eight working days in both copies. The fixed one-day allowance remains one day, while a quarter of the revised duration is two days. Compare the actual planned offsets, allowing for the working calendar, instead of counting blank calendar squares around a weekend.

The two plans answer different questions. “Wait one working day after the draft finishes” preserves an interval. “Begin while the final quarter is still scheduled” preserves a proportion. Do not choose the one producing the earlier finish unless that rule describes the real work.

Check the operational meaning of overlap

For a real review, identify what portion of the draft must be available before the reviewer starts. A percentage of scheduled time does not establish that the necessary pages, data or approvals exist. If the work cannot be divided as assumed, revise the dependency design with the responsible people.

Keep a short explanation beside the offset: its sign, unit, predecessor and rationale. Recheck after changing duration estimates. The accepted plan should remain understandable when someone else reads the dependency fields, without needing to reconstruct why a bar was once dragged to a particular date.

Sources: Microsoft: lead and lag; Microsoft: Project Step by Step: dependency offsets.