Comment by georgefrowny

Basically there is no universal ID system. You are not required to have a passport or driving licence, which are the usual IDs. There is an optional kind of ID you can use to prove your age if you don't or can't have those. Even if you do have one of these, you don't have to show it to the police if they stop you. The police can ask your name, but unless the police has "reasonable grounds" to search you, you can just walk away.

This is at odds to much of the EU where carrying ID is normal and you can be fined for not having it on you in public.

Proving your identity to a company usually involves a copy of passport and a recent utility bill. Sometimes you need to get a "professional" (doctor, lawyer) to write "I certify this is a valid copy" on it. Financial systems often use your NI number (think SSN) as the ID factor for things like KYC, the NHS uses a separate number. There are several fairly mysterious companies that provide this service to companies who need to know like solicitors (you upload the photos, they authenticte it "somehow", hopefully they look after it, presumably they can be audited I turn out to be a money launderer using a fake document). Getting a passport is a bit of a performance as you have to bootstrap the trust chain by getting someone you know to submit their documents and vouch for your photos.

It also means that, to use a hot-button subject recently, the police have limited practical ways to prove a right to work, unless they have strong intelligence that a particular place is using illegal labour and do a raid. The current tactic seems to be arresting people for illegal e-bikes, where they have reasonable grounds for an arrest and can then get the name and do the immigration checks at that point.