This note outlines the registration and other formalities for perfecting a security interest over freehold or leasehold property (also known as real estate). The registration and other formalities include whether the security interest needs to be contained in a document executed as a deed or be in writing, registering the security interest at Companies House and the Land Registry and serving notices on landlords and prior mortgagees. The perfection requirements for a range of security interests are covered, including legal mortgages, equitable mortgages, fixed charges, floating charges and liens.