Is it illegal to not carry ID in the UK?

Unlike many European countries, the United Kingdom does not have a compulsory identity card scheme. The Identity Cards Act 2006, which introduced a national identity card, was repealed by the Identity Documents Act 2010. There is no general obligation to carry or produce identification documents.

During a stop and search or a police encounter, officers may ask for your name and address, but you are not legally required to provide this information in most circumstances. The exception is when you are arrested (PACE Code C requires you to be asked your name and address at the police station) or when specific statutory obligations apply.

For driving, the position is different. Under s.164 of the Road Traffic Act 1988, a constable may require a person driving a motor vehicle on a road to produce their driving licence. If you cannot produce it immediately, you are given a "producer" (an HORT/1 form) requiring you to present the licence at a police station within seven days. Failure to produce a licence when required is an offence.

Similarly, under s.165 of the Road Traffic Act 1988, a constable may require production of a certificate of insurance and an MOT certificate.

For persons under 18 attempting to purchase alcohol, the Licensing Act 2003 s.149 makes it an offence to sell alcohol to a person under 18, and retailers routinely require proof of age. However, this is a condition of the sale, not a legal requirement to carry ID.

For foreign nationals, the Immigration Act 1971 requires a person subject to immigration control to produce documents on request by an immigration officer (not a police officer, unless immigration powers are engaged). However, this does not apply to British citizens or persons with settled status.

In summary: you cannot be penalised for not carrying ID in everyday life in England and Wales. There is no "papers, please" power.