The Mental Capacity Act (MCA) 2005 came into force in 2007 and covers England and Wales. It provides a statutory framework for anyone over the age of 16 who lacks capacity to make decisions for themselves, for whatever reason. The MCA was drafted by the Law Commission partly in response to the increased prevalence of dementia and the lack of legislation to deal with the challenges of so many people living longer and losing their ability to make decisions. It is the loss of ability to make decisions, because of the disease, which makes the key link between providing care and treatment with the application of the law. This is why the MCA is perhaps the most important of all the pieces of legislation we consider. The practical applications of the Act will be dealt with in more detail in the chapters to follow. More detailed guidance can be found in the Mental Capacity Act 2005: Code of Practice (for England and Wales), revised in 2022. We include some of the main amendments to the Code at the end of this chapter and these are also covered in the relevant sections of the book.