Timeline for COS assignment

[colingtha]

Can the employer assign the COS (Certificate of Sponsorship) more than 3 months prior to the start date?

Is there the earliest sensible date when the COS can be assigned (I assume it should be ~5 months prior to the start date)?

I understand that once the COS is issued one has to use it within 3 months and one cannot submit a visa application more than 3 months prior to the start date indicated in the COS.

As it might take several weeks to approve the COS it would make sense for the employer to submit an application for the COS in advance so the applicant could apply for a visa at the earliest - 3 months before the start date.

Thanks very much.