The new rules, expected to save Britain 500 million pounds, will apply to non-emergency treatments as part of a clampdown on so-called health tourists who have so far been able to leave the country without paying for such treatments.
"We have no problem with overseas visitors using our NHS - as long as they make a fair contribution, just as the British taxpayer does," UK health secretary Jeremy Hunt said.
Tourists to the UK have always been expected to pay for NHS treatments but were billed only after the procedure, leading to a large unpaid bill for the taxpayer-funded health service.
The new pre-payment process will be enforced to tackle this problem.
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It will be up to individual NHS Trusts to work out whether they take a payment there and then or allow patients to sign a form to agree to a longer-term payment plan.
Under the new plans, anyone from outside the European Economic Area (EEA) - which includes Indians - staying in the UK for longer than six months will also not be eligible for free fertility treatment on the NHS.
Those needing urgent care will still be treated immediately as part of the Accident & Emergency (A&E) services provided by the NHS.
Such emergency patients will be invoiced later if they are found to be non-UK taxpayers and therefore not eligible for free care in the country.