Businesses in England and Wales that allow under-18s to use sunbeds risk being fined up to £20,000 under new legislation.
The Sunbed (Regulation) Act 2010 stops young people using sunbeds in places including salons, gyms and hotels.
However, there will be no requirement for businesses to ask for ID, or to keep a register of customers.
Cancer experts said the move would help protect children from developing skin cancer in later life.
Figures show that, on average, 6% of 11 to 17-year-olds in England use sunbeds, rising to 50% of 15 to 17-year-olds girls in Liverpool and Sunderland.
Data published by Cancer Research UK earlier this week showed more than two people under the age of 35 are diagnosed with malignant melanoma - the deadliest form of skin cancer - every day in the UK.
It will be up to local authorities to decide how to check businesses are complying with the law, using measures such as unannounced spot-checks or pre-planned visits.
Members of the public will also be able to report concerns over a business allowing children and adolescents to use sunbeds.
The Chartered Institute of Environmental Health (CIEH) said the ban would help protect young people, but said it did not go far enough.
It called for similar measures to those in Wales, where use of unsupervised machines is also banned and businesses are required to provide health information and protective eyewear to customers.
Andrew Griffiths of the CIEH, said: "We are extremely pleased to see the Act coming into force and believe it will give valuable protection to young people who are particularly vulnerable when it comes to contracting skin cancer."
Scotland banned under-18 sunbed use in 2008. The Northern Ireland Assembly has also proposed a ban.
Announcing the English legislative change, public health minister Anne Milton said: "This new law will go some way to help reduce one of the biggest cancers among 15 to 24-year-olds.
"We want to protect under-18s from the dangers of sunbeds and reduce the number of young people getting skin cancer."
Cancer Research UK's director of policy, Sarah Woolnough, said: "The World Health Organization has classified sunbed use in its highest risk category for cancer, alongside tobacco.
"We encourage people to take care in the sun and avoid using sunbeds."
Dr Elizabeth Rapley, from the Institute of Cancer Research, added: "Using sunbeds under the age of 35 increases the risk of developing malignant melanoma by 75%.
"This law will go a long way to protecting children from developing malignant melanoma in later life."