Milestone slip charts are designed to give an at-a-glance overview of how your project is doing. They do this by plotting the predicted delivery date for each milestone at every project status report.

These charts are ideal for importing into project dashboards because, as we will see, they show history very well. They are also known as Milestone Tracking Charts.

Down the left hand side of the chart we show the date that updates to the estimates were made. Usually this will match up with the dates that you are preparing reporting information - in this case August 4th and September 1st.

Along the top we show the date that was estimated at that update. You can see that for Milestone 2 () the estimated dates were the same, so we get a nice vertical line. However our estimate for completion of Milestone 1 () has now changed from September 14th to September 19th. This is made really obvious on the chart by the slope of the line.

In order to be able to see this from a regular reporting pack you would need a good memory or both packs in front of you. This chart provides the history at a glance - which gets more useful as the project goes on. Let's look at the update for today.

We can see that once again Milestone 1 () has slipped and needs 'just a few more days' to complete. Because it's so close, though, we can be pretty sure that it's being managed. More worrying is Milestone 2 () - it was going to deliver three weeks after Milestone 1, now it's going to be done in two weeks? Better ask some questions about that otherwise when we get to the next update...

We can see that Milestone 1 () did deliver, but that a follow on slip to Milestone 2 () has been identified - a surprise they could have avoided by seeing the right data sooner.

If you are a project sponsor then asking to see a milestone slip chart each month will give you better visibility of schedule slips. If you are a project manager then it can work for you too, by uncovering problems while you still have time to do something about them!

(The Plan Is offers a free milestone slip chart drawing tool - try it for yourself and let us know what you think! You can reach us on Twitter via @theplanis.)