Just checked it out (I was intrigued) on Companies House
"2. Where must I display my company name?
Every company, unless it has at all times been dormant since incorporation, must display a sign with its registered name at:
its registered office;
any inspection place;
at any location at which it carries on business (unless it is primarily used for living accommodation.
It must also include its registered name in all business communications (hard copy and electronic)."
There must be other rules though as that would mean that accounts would have to display all company names that are registered at their premises (and they dont)
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Bookkeeping and payroll services in and around Swindon www.m4books.com
..but they should! Most have a list on the wall by their front door, inside the office..this came into effect only recently with all the changes so many will prob not know about it!