How to Review a Subcontractor Schedule Update

When a subcontractor submits a schedule update, most project managers do one of two things: they glance at the dates to see if the completion milestone moved, or they forward it to the scheduler and assume everything is fine. Neither approach is adequate.

Subcontractor schedule updates are where schedule manipulation most commonly occurs — and where the documentation failures that hurt you in a dispute most often originate. A structured review process takes less time than you think and produces a record that is worth its weight in any future disagreement.

This post walks through a practical, step-by-step approach to reviewing a subcontractor schedule update.

What You Are Looking For

A subcontractor schedule review has four objectives:

1. Confirm the update is current — the schedule reflects actual progress as of the data date
2. Identify what changed — every modification from the previous approved schedule
3. Assess whether changes are authorized — changes that were not agreed to in a schedule revision request are a problem
4. Document your findings — your review needs to be on record, not just in your head

Step 1: Check the Basics Before Anything Else

Before reviewing the content of the schedule, confirm the administrative basics:

Data date. The data date should match the reporting period. A schedule submitted for the end of March with a February data date has not been properly updated. In P6, the data date is the PROJECT.last_recalc_date field. Change Inspector's Dashboard shows this prominently.

Recalculation. Confirm the schedule has been recalculated after the last status update. A schedule with stale CPM dates — float values and early/late dates that do not reflect the current data date — is not a valid update.

Activity count. Note how many activities are in the schedule compared to the previous submission. A significant change in activity count without explanation is a flag.

Scheduled completion. Has the overall project completion date moved? Even a small movement deserves an explanation.

Step 2: Run a Comparison Against the Previously Approved Schedule

The most efficient way to review a subcontractor update is to run a schedule comparison between the current submission and the last approved schedule. This instantly surfaces every change — added activities, removed activities, modified dates, changed logic, float movement — without requiring you to manually read through two schedules.

In Change Inspector, load both files and go to the Compare module. Work through the tabs in this order:

Schedule Options first. Check whether any P6 calculation settings changed — retained logic, float type, critical float threshold. If settings changed without notice, that needs an explanation before you review anything else.

Activities tab. Filter to show Added, Removed, and Changed activities separately. Review each category:

• Added activities: are they properly connected to the network? Do they have reasonable durations? Were they authorized?
• Removed activities: why were they removed? Were they completed, or were they deleted to hide a problem?
• Changed activities: focus on critical and near-critical activities first. Date changes, duration changes, and status changes on these activities have immediate schedule implications.

Relationships tab. Logic changes are the most commonly overlooked category in subcontractor reviews. A predecessor relationship that gets removed or modified can shift the critical path without any date on any individual activity obviously moving. Review every changed relationship, particularly on critical activities.

Gantt Diff. Sort by Delay to see which activities have moved the most relative to the previous submission. This gives you a quick visual picture of where the schedule shifted.

Step 3: Check for Specific Red Flags

Beyond the general comparison review, look specifically for these patterns:

Float manipulation. Has total float increased on activities that should be progressing normally? An activity gaining float between updates — rather than consuming it — may indicate that a constraining predecessor was removed or that the activity's duration was reduced without a legitimate basis.

Baseline changes. The approved baseline should not change without a formal schedule revision request. If baseline dates have shifted, that is an unauthorized change regardless of whether the current schedule looks acceptable.

Out-of-sequence progress. Activities showing as complete or in progress that should not have started yet based on their predecessors — this indicates either out-of-sequence work (which may be legitimate and may not) or status update errors.

Missing resources. If the schedule was previously resource-loaded and resources have been removed, that is a material change to the schedule's usefulness as a planning tool.

Constraint additions. New hard constraints — Must Start On, Must Finish On — that were not in the previous submission are a flag. They may be masking float problems by forcing activities to specific dates.

Step 4: Document Your Findings

Your review is only useful if it is documented. A verbal conversation with the subcontractor scheduler is not a record.

Export the comparison results from Change Inspector to Excel. Note your specific findings — which activities changed, whether the changes were authorized, what questions you are raising, and what response you expect. Send this to the subcontractor in writing and retain a copy in the project file.

If you are accepting the schedule as submitted, note that acceptance in writing and attach the comparison report. If you are requesting revisions, be specific about what needs to change before you will accept the update.

This documentation habit takes an extra 20 minutes per review cycle. In a dispute situation, it is often the difference between having a defensible record and having nothing.

Step 5: Maintain the Schedule Log

Add every submitted schedule to a running log — the submission date, the data date, the status (accepted, rejected, under review), and any notes about significant changes. Change Inspector's Schedule Log module does this automatically when you load files in sequence and exports the log to Excel.

The running log is what makes the comparison history useful months later. When a dispute arises at month 14 of an 18-month project, you need to be able to show the complete picture of how the schedule evolved — not reconstruct it from memory.