Requirement to give security: serving the Notice of Requirement to give security (NOR): service by post
If personal service is not possible you can serve a Notice of Requirement (NOR) by post using recorded delivery.
For guidance on where and on whom to serve the notice, see SG43100.
The NOR is signed and dated with the date of posting. An NOR can be served by post to the person at their last or usual residence, or place of business. Using recorded delivery confirms the date on which the person receives the NOR.