Company Secretary Termination UK "My Own!"

Suggest you talk to Companies House and / or your local Business Link on this one. They're both helpful. Remember to keep notes of your conversation and their guidance - preferably get the advisor(s) to confirm their guidance in writing.

As far as I know, once you've formally stated in writing to the relevant Directors that you're resigning from the Company Secretary post as from a specific date, then you've resigned and are free from any subsequent obligations. This is only an opnion, however, which you'd need to check with the experts.

site: Welcome to Careers Partnership (UK) | Careers Partnership (UK)
blog: Blog | Careers Partnership (UK)

I thought it was normally the MD that filled in the 288b, but as said, as long as you have written to the directors and confirmed your termination, I would assume it would be their responsibility.

As for multiple directorships or director and comp sec of different businesses, no worries there.