The principal contractor is the contractor appointed to control the construction phase where more than one contractor is involved. The role exists under the CDM Regulations 2015 and is reinforced by the Building Safety Act, which requires the appointment to be made in writing.
Duties include planning, managing and monitoring the construction phase, coordinating other contractors, and, for higher-risk work, operating a mandatory occurrence reporting system. At the end of the appointment the principal contractor must hand over the information it holds so the record is not lost.
Because the appointment is triggered simply by having more than one contractor on a project, it reaches far more than large sites. The evidential expectation is that the principal contractor can show what happened and produce the record on request.