You can lock the phases on a job to ensure posting only occurs to phases/cost types assigned to the job.

When you select the Phases on this job are locked checkbox in JC Jobs, you lock the job so that you can only post to phases assigned specifically to that job in JC Job Phases, JC Original Estimates, or JC Change Orders. This can help prevent accidental posting to phases not estimated for the job.

In addition, phase lookups (accessed by pressing F4 in any Phase field) will display only those phases set up in JC Job Phases; they will not display phases in JC Phases. If you need to add a phase to a locked job, and you have permission to run the JC Job Phases form, you can press F5 in the Phase field on any posting screen to access JC Job Phases and add the phase.