It is a one-off policy that covers a gap in the paperwork rather than a fault in the property. The usual trigger is a missing building regulations certificate for work done years ago, or an alteration nobody documented at the time. Rather than hold everything up chasing the council, an indemnity policy protects you against enforcement action, and most lenders accept it. Premiums are usually modest. Your solicitor should tell you when it is the sensible answer and when it is papering over something worth investigating properly.