The NHS surcharge was introduced by the Immigration Act 2014 to ensure that non EEA nationals who apply for a visa of more than 6 months duration make a financial contribution in order to benefit from its services.
A fee of £200 (£150 for a Tier 4 migrant) for a whole or each part of year must be paid as part of the respective immigration application, unless one of the following exemptions applies:
If you fail to make the application a caseworker should request payment of the fee, if you are within the UK this must be paid within 10 working days and 7 working days if outside the UK, otherwise the entire application will be rejected.