The wage increase is expected to give 1.8 million workers an immediate pay rise.
The policy was announced in last summer's Budget by Chancellor George Osborne, in an effort to create a higher-wage, lower-welfare economy.
The wage increase will result in 60,000 fewer jobs and increase business costs by around 1 per cent of corporate profits, according to the Office for Budget Responsibility.
"It will also mark the end of the gender pay gap for some of our lowest paid and hardest working people," he said.
Workers aged 21 to 24 will continue to be paid the National Minimum Wage of 6.70 pounds an hour.
Some 1.3 million workers are paid the minimum wage, while another 500,000 who earn slightly more than the current 6.70 pounds an hour will also benefit.
Ryan Bourne, head of public policy at the Institute of Economic Affairs think-tank, said: "Its introduction will make it too expensive for some businesses to take on young, low-skilled workers in jobs that provide essential experience. It is these vulnerable people who will be hit the hardest".
