REACH Pre-registration is needed for existing substances.
Pre-registration distinguishes between ‘phase-in (i.e. existing) substances’ and new substances.
Without REACH pre-registration, the competent authorities may demand immediate registration; even for an existing substance. If a chemical is not pre-registered, it cannot be marketed safely.
Even if there is no intention to actually register a substance (as may be the case for importers of mixtures) it should still be pre-registered. This is necessary to avoid being obliged to register at a very inconvenient moment.
REACH Pre-Registration of a substance does not imply that the substances must also be registered.