Every cut-off it's the same routine. The contractor sends over an updated schedule, and someone on the project controls team has to work out whether to trust it. Did the logic change somewhere? Did activities slip without anyone raising a claim? Did the costs jump between revisions? Doing that review by hand means opening two schedules in Primavera P6 and flicking back and forth between them. It's slow, it's easy to miss something, and good luck evidencing any of it a year later.
Here's the good news: you don't need to open P6 to do this. With Plexxel's P6 Schedule Comparison tool you load the baseline and the update, click once, and get a clean Excel report of everything that changed between them. Below I'll walk through the process, and more importantly, what you should be looking for once you have the report in front of you.
The scenario: a typical monthly submission
Say your last approved revision was dated 30 November, and the contractor has just sent over the 28 December update. A normal monthly progress cut. Both are P6 schedules exported as XER files, and your job is to confirm that the changes between them are real, justified, and line up with what actually happened on site.
Running the comparison
The mechanics take about thirty seconds. From the Plexxel ribbon in Excel:
- Open the P6 Schedule Comparison tool from the Plexxel ribbon.
- Load your two XER files: the baseline (30 Nov) and the update (28 Dec).
- Choose where you'd like the report saved.
- Click Compare. Plexxel parses both schedules and writes a structured summary to Excel in seconds.
Tip: Keep every monthly comparison report in a dated folder. Over the life of a project that turns into a ready-made audit trail, and you'll be very glad of it if a delay claim ever lands on your desk.
What the report actually tells you
A comparison is only as good as the questions you bring to it. Here are the five things I check on every update. Plexxel calls each one out in the report, so you're not left hunting around for them.
1. Logic & relationship changes
Look for relationships that were added, deleted, or re-typed: an FS flipped to FF, a lag slipped in, a link taken out. These are the changes most likely to move the schedule without an obvious reason, so they're the first thing to check against whatever story the contractor is telling. Out-of-sequence progress gets flagged here too.
2. Cost & resource variance
Did budgeted or actual cost jump between revisions when you weren't expecting it? Compare labour and non-labour resource units side by side, and make sure any big reallocation has a real reason behind it and isn't just a quiet re-baseline.
3. Total float & critical path shifts
Watch for movement in total float and shifts in which activities are driving the completion date. If the critical path has rerouted itself, or early and late dates have moved further than a single month of progress should allow, that's worth a closer look.
4. Start / finish date overrides
Find where actual start or finish dates have been overridden. Every override should match your site records. If a date moved but the progress didn't, that's a gap worth raising before you accept the update.
5. Earned value vs. actual progress
Finally, sanity-check reported progress against earned value. Mismatches and negative variances are exactly where over-claiming tends to hide, so this is your evidence base for backing up (or pushing back on) the contractor's performance figures.
Why do it in Excel at all?
Because the review needs to be fast, repeatable, and something you can defend later. Doing it inside Excel with Plexxel means you can:
- Cut hours of manual cross-checking down to a single click each month.
- Get clear, structured variance output instead of squinting at two Gantt charts.
- Make review decisions on accurate data rather than gut feel.
- Keep a paper trail that backs you up if a delay claim ever comes your way.
Note: P6 Schedule Comparison is part of Plexxel Pro. The free version already gives you the XER Schedule Audit, WBS tools, PMS sheets and Gantt charts, so you can start checking schedule health today and upgrade once you need the full comparison report.
Review your next update in minutes, not hours
Download Plexxel free, or unlock P6 Schedule Comparison and the full Pro toolkit for $25/year.
Ali, Founder of Plexxel
I'm a planner, and I built Plexxel to take the grunt work out of project controls. If a feature could save you an hour this week, that's the whole point. Questions? Just email support@plexxel.com. It comes straight to me.