Turn off Auto Compute Actuals for 1 activity

By default, most Primavera P6 projects enable the option:

“Recalculate Actual Units and Cost when Duration % Complete changes.”

With this setting turned on, whenever you update Duration % Complete, P6 automatically recalculates and updates the Actual Units. This is useful in many cases, as it keeps progress and resource usage aligned.

In some situations, you may want to update Duration % Complete without affecting Actual Units.

You can disable this option at: Project → Calculations → uncheck the option

However, this change applies to the entire project, which may not be suitable if you only want to control it for a specific activity.

Another method is to go to the Resource Dictionary and disable the setting there.

But again, the limitation is:

It applies to all assignments of that resource across the project.

Not just a single activity.

If you want to control this behavior for only one activity, there is a practical workaround.

The key observation is:

The option “Recalculate Actual Units and Cost when Duration % Complete changes” does not affect activities with Duration Type = “Fixed Units” or “Fixed Units/Time.”

What You Can Do: