All advertisements require Advertisement Consent either from the local planning authority unless it is automatically permitted by virtue of planning legislation. This is known as “deemed consent”
For example, many traditional, non-illuminated fascia signs and hanging signs are likely to have deemed consent subject to a number of conditions and limitations such as size.
If an advert meets all the criteria of deemed consent you will not require express consent from the Local Planning Authority.
Read 'Outdoor advertisements and signs: a guide for advertisers' for a detailed explanation of the planning regime for adverts and signs.
The specifics of deemed consent are detailed in Part 2 of The Town and Country Planning (Control of Advertisements) (England) Regulations.
Because inappropriate adverts can harm an area visually (and even economically) many authorities have produced supplementary guidance on the design of suitable adverts and commercial signage.
Other adverts without deemed consent will require express advertisement consent from the local planning authority. If the building is listed you will also require Listed Building Consent.
The display of an advert without consent is a criminal offence, so you must always ensure that you have the appropriate consent, or the Local Planning Authority may take action to secure its removal, including prosecution.
You may also require the consent of the landlord or landowner.