Overview
A restriction is the REACH tool that limits or bans a substance directly. The rules sit in Annex XVII. When a substance is restricted for a use, the limit applies on its own. There is no application to file and no permission to wait for.
This makes restriction the blunt, broad instrument of REACH. It is used when a risk needs to be controlled across the whole EU market rather than handled company by company.
How it differs from authorisation
The limit applies directly to everyone for the listed uses. No one applies for anything. If you are within scope, you comply.
Use is banned after a sunset date unless a company applies and the Commission grants permission for that specific use.
A typical Annex XVII entry names the substance, the uses concerned and any concentration limit, for example a maximum percentage allowed in a consumer article. See the REACH annexes for how this fits with authorisation.
Note: general educational information, not legal advice. Check the official source before relying on it.