To make sure the NHS remains free at the point of delivery and access to NHS services is based on clinical need, but not an individual's ability to pay, guidance states that the NHS should never subsidise private care with public money.
This means “co-funding”, which is when both private and NHS funding is used for a single episode of care, is not permitted under NHS rules. Any additional private care must be delivered separately from NHS care. In line with NHS guidance, NHS Kent and Medway only supports shared care to be undertaken with an NHS commissioned provider providing an NHS service.
This means, for instance, that all patients who receive a private assessment or diagnosis for a condition that results in needing a prescription for ongoing medication will need to be referred into an NHS commissioned service for ongoing prescribing to continue within the NHS.
If a patient seeks assessment or diagnosis privately or through a provider acting in a private capacity (non-NHS) the GP is under no obligation to continue to prescribe treatment.
You can read more about this on the gov.uk website.