The Organ Donor Register and National Transplant Register is run by the NHS. The service matches donors to people who are in desperate need of a transplant.
In 2016/2017 ore transplant operations took place than ever before, but the health service says many more people are waiting for life-saving surgery.
Around 6,500 people are currently on the UK transplant waiting list.
In 2017, nearly 500 people died while waiting for a transplant.
You can register to become an organ donor at any age.
The NHS advises that underage donors make their family aware of their wishes to donate their organs, as guardians or parents will be asked to give permission on your behalf, until you the reach legal age.
The legal age varies depending on whether you live in England/Wales, Northern Ireland or Scotland.
There is no upper age limit for donation.
It is down to clinical staff to decide which organs are suitable for donation.
Earlier this year, research found almost three-quarters of English people are in favour of an opt-out organ donor system.
A survey by the British Heart Foundation (BHF) found that 74% of people are in favour of a system where people are registered as a potential donor unless they state otherwise.