The Institute has sixteen Regions and two Centres. The Regions are sub-divided along county lines into numerical groups and the Centres are those based overseas, namely Hong Kong and the Republic of Ireland.
All members are allocated to a Region or Centre upon joining, dictated by the county in which they reside (although the member can elect to change Regions/Centre). The Regions and Centres do not have their own individual administrative offices or paid staff. Each Region and Centre has a Committee which are all members from that Region/Centre who have put themselves forward in a voluntary capacity.

Each Regional/Centre Committee is comprised of up to twelve members, from which the following positions are elected: