Internal tasks not visible to external parties

I would like to have some tasks in a planning that are related to internal actions but I wouldn’t like our clients to see them in the planning as we print it out.
Is it possible to do this with some specific feature of the programme or do I have to use some strategies?
Thank you.

@Diana If these tasks are named in a specific way, or assigned to a specific resource, you could filter the view in OmniPlan before printing. Information about working with filters in OmniPlan is available here: