Definition
A statutory document issued by your Building Control body confirming that the work, as inspected, complies with the Building Regulations in force at the time.
Why it matters
Conveyancing, mortgages, insurance and resale all turn on it. Without one, every future buyer's solicitor will ask why — and ask you to fix it before they exchange.
Getting it
Final inspection, all non-conformities cleared, and the relevant trade certificates submitted. Until it is in your file, the project is not complete.