"I thought" does not do. You must read your Code of Conduct as adopted by your council. Mine has a schedule showing what interests must be declared and where and when. Interests can be other than pecuniary. For example, a councillor should declare an interest in his son's planning application, or his very close friend's. Anything that might lead to a prejudice or bias is an interest.They may or may not be noted but they must be declared as and when relevant. If they are noted it should be on the county register and in the public domain. There is no other official register. Scrappy note books held by clerks are not official. The interests must not be kept secret as that, obviously, defeats the whole purpose.