The next national census is to include a controversial question about gender identity for the first time.
MPs have given the go ahead for the Office for National Statistics (ONS) to formally ask citizens if their preferred gender identity matches their birth sex.
The ONS says this will help them to determine the number of people who say they are transgender in the population.
Compulsory
A report by MPs suggested there are 650,000 people in the UK who do not identify as their birth sex.
However, only around 5,000 people have obtained a Gender Recognition Certificate (GRC) from the Government to say they have changed legal sex.
The question about gender identity will be voluntary, while the question about birth sex will remain compulsory.